I did some tests on this. Here I show what I did and the results with the stock Clock app on an LG on Marshmallow. I would appreciate if someone can confirm these results on either Marshmallow or whatever.
First, essentially important, notice that there is a *difference* between pressing snooze, and ignoring. If you just ignore the ring and let it ring out (for me, that's 60 seconds), it "self-snoozes". Note below that a self-snooze and a snooze Press are not the same for alarm self-dismissal.
Short answer: after SIX consecutive ringings (thus 5 snooze periods) without a keypress, it gives up and self-dismisses.
At least on MY phone this is verified. The alarm self-dismisses after you ignore SIX consecutive rings without pressing anything. However every time you PRESS snooze, as long as you haven't missed 6 chances in a row yet, you effectively reset the counter; and the alarm can be continued indefinitely (well, I'll just say, 6 hours is as far as I've tested), until it does get six consecutive rings without a button press.
As a practical example, if my daily 6 A.M. wake-up alarm has snooze set to 5 minutes, and I never get up to PRESS snooze, at 6:26 the alarm will give up and self-dismiss. (For a snooze setting of 15 minutes, that would be 7:16.) But had I touched the snooze button on any of those 6 chances (i.e., between 6:00 and 6:26), I would have "bought myself" another 30 minutes before the alarm self-dismissed. And if I *pressed* Snooze anytime during THOSE 30 extra minutes, I would "extend my life" for yet another 30 minutes. I haven't managed to find any limit as to those extensions (though I suspect it's 12 or 24 hours). I once pressed snooze every 15 minutes for 6 hours before I dismissed it myself.
So if you don't touch anything, you will get 5 snooze periods (I prefer to say "self-snooze" periods), which means ignoring the alarm 6 times, before self-dismissal. After the 6th time ignoring (you ignored the initial alarm, and each of them following the next 5 snooze periods), it self-dismisses, and reports the dismissal in the notification area.
For example, if you have a 5 minute snooze setting on at alarm set for 1:00, and you ignore the 1:00 dismiss/snooze screen, and you also ignore it at 1:05, 1:10, 1:15, 1:20, and 1:25, that makes 6 in a row that you ignored, so at the end of the 1:25 ringing it self dismisses. (For me that means it self-dismisses at 1:26, because my alarms run for 60 seconds before self-snoozing.)
Note that I can respond to OTHER alarms that arise between the snoozes. I can snooze or dismiss a DIFFERENT alarm at 1:02 and the 5 snooze period lifetime for the alarm we're discussing is unaffected.
When you DO *press* "snooze", the 5 period limit is reset. You buy yourself another 5 self-snooze periods (plus one minute, or however long the alarm goes before self-snoozing). Every time you press snooze, you buy yourself another 30 minutes in this example. If at any point you ignore the one 5 minutes after touching snooze, and ignore 10 minutes after,15,20,25,30 - that makes 6 in a row - and one minute later, it "self-destructs."
Here is an example of never responding to a 1:00 alarm and after 6 times ignoring, self-dismissal:
self snoozed 1:00 (ignore #1 )
self snoozed 1:05 (ignore #2 )
self snoozed 1:10 (ignore #3 )
self snoozed 1:15 (ignore #4 )
self snoozed 1:20 (ignore #5 )
last chance alarm at 1:25 (You don't take it, and do ignore #6 )
SELF-DISMISS at 1:26
But when this same alarm happened the next day, I snuck in at the last chance, after ignoring only 5 in a row, and pressed snooze myself when the 1:25 alarm was ringing; and you will see that it bought me another 31 minutes - at which time I finally DID reach the fatal 6 ignored alarm rings in a row, and self-dismissal occurred:
self snoozed 1:00 (really 1:01) (ignore #1 )
self snoozed 1:05 (ignore #2 )
self snoozed 1:10 (ignore #3 )
self snoozed 1:15 (ignore #4 )
self snoozed 1:20 (really 1:21) (ignore #5 )
HAND snoozed at 1:25 (just before the option to prevent self-destruction expired at 1:26!)
self snoozed 1:30 (really 1:31) (ignore #1 )
self snoozed 1:35 (ignore #2 )
self snoozed 1:40 (ignore #3 )
self snoozed 1:45 (ignore #4 )
self snoozed 1:50 (really 1:51) (ignore #5 )
last chance alarm at 1:55 (which you ignore, #6 )
SELF-DISMISS at 1:56
For all I know this rule may vary with other installations, but it might be the rule for everyone using the stock Clock. Let me know!
First, essentially important, notice that there is a *difference* between pressing snooze, and ignoring. If you just ignore the ring and let it ring out (for me, that's 60 seconds), it "self-snoozes". Note below that a self-snooze and a snooze Press are not the same for alarm self-dismissal.
Short answer: after SIX consecutive ringings (thus 5 snooze periods) without a keypress, it gives up and self-dismisses.
At least on MY phone this is verified. The alarm self-dismisses after you ignore SIX consecutive rings without pressing anything. However every time you PRESS snooze, as long as you haven't missed 6 chances in a row yet, you effectively reset the counter; and the alarm can be continued indefinitely (well, I'll just say, 6 hours is as far as I've tested), until it does get six consecutive rings without a button press.
As a practical example, if my daily 6 A.M. wake-up alarm has snooze set to 5 minutes, and I never get up to PRESS snooze, at 6:26 the alarm will give up and self-dismiss. (For a snooze setting of 15 minutes, that would be 7:16.) But had I touched the snooze button on any of those 6 chances (i.e., between 6:00 and 6:26), I would have "bought myself" another 30 minutes before the alarm self-dismissed. And if I *pressed* Snooze anytime during THOSE 30 extra minutes, I would "extend my life" for yet another 30 minutes. I haven't managed to find any limit as to those extensions (though I suspect it's 12 or 24 hours). I once pressed snooze every 15 minutes for 6 hours before I dismissed it myself.
So if you don't touch anything, you will get 5 snooze periods (I prefer to say "self-snooze" periods), which means ignoring the alarm 6 times, before self-dismissal. After the 6th time ignoring (you ignored the initial alarm, and each of them following the next 5 snooze periods), it self-dismisses, and reports the dismissal in the notification area.
For example, if you have a 5 minute snooze setting on at alarm set for 1:00, and you ignore the 1:00 dismiss/snooze screen, and you also ignore it at 1:05, 1:10, 1:15, 1:20, and 1:25, that makes 6 in a row that you ignored, so at the end of the 1:25 ringing it self dismisses. (For me that means it self-dismisses at 1:26, because my alarms run for 60 seconds before self-snoozing.)
Note that I can respond to OTHER alarms that arise between the snoozes. I can snooze or dismiss a DIFFERENT alarm at 1:02 and the 5 snooze period lifetime for the alarm we're discussing is unaffected.
When you DO *press* "snooze", the 5 period limit is reset. You buy yourself another 5 self-snooze periods (plus one minute, or however long the alarm goes before self-snoozing). Every time you press snooze, you buy yourself another 30 minutes in this example. If at any point you ignore the one 5 minutes after touching snooze, and ignore 10 minutes after,15,20,25,30 - that makes 6 in a row - and one minute later, it "self-destructs."
Here is an example of never responding to a 1:00 alarm and after 6 times ignoring, self-dismissal:
self snoozed 1:00 (ignore #1 )
self snoozed 1:05 (ignore #2 )
self snoozed 1:10 (ignore #3 )
self snoozed 1:15 (ignore #4 )
self snoozed 1:20 (ignore #5 )
last chance alarm at 1:25 (You don't take it, and do ignore #6 )
SELF-DISMISS at 1:26
But when this same alarm happened the next day, I snuck in at the last chance, after ignoring only 5 in a row, and pressed snooze myself when the 1:25 alarm was ringing; and you will see that it bought me another 31 minutes - at which time I finally DID reach the fatal 6 ignored alarm rings in a row, and self-dismissal occurred:
self snoozed 1:00 (really 1:01) (ignore #1 )
self snoozed 1:05 (ignore #2 )
self snoozed 1:10 (ignore #3 )
self snoozed 1:15 (ignore #4 )
self snoozed 1:20 (really 1:21) (ignore #5 )
HAND snoozed at 1:25 (just before the option to prevent self-destruction expired at 1:26!)
self snoozed 1:30 (really 1:31) (ignore #1 )
self snoozed 1:35 (ignore #2 )
self snoozed 1:40 (ignore #3 )
self snoozed 1:45 (ignore #4 )
self snoozed 1:50 (really 1:51) (ignore #5 )
last chance alarm at 1:55 (which you ignore, #6 )
SELF-DISMISS at 1:56
For all I know this rule may vary with other installations, but it might be the rule for everyone using the stock Clock. Let me know!