Does it makes sense to buy spare battery for my Nexus 6

[Mahesh Abnave]

My Nexus 6 is 3.5 years now.
I still use it as daily driver.
I keep it on power saving mode all time.
I have only needful apps installed. (Only WhatsApp in social media department.)
Whenever I am to lock my mobile, I ensure that I stop unnecessary services by going to Settings > Developer Options > Running Services
This way I am able to extend my battery life to at least 1 full day and even more.

Point is that I love this device too much. I have beefy Supcase Unicorn Beetle Pro cover installed on it. Hence the phone itself is in pristine condition. I may replace this phone in some months or years, but not decided yet. But even after that I want to use it as a media consumption device (streaming to chromecast, browsing, music, I dont watch movies much, neither play games).

One day the phone battery will die badly, and may not work even in the way I am using it now (all times power saving mode). So I want to ask if I should buy a spare battery upfront now and keep it stocked and repalce it whenever current one dies fully? (I dont want to replace it now, because I dont want to risk opening my phone now and also because I am currently able to use it in the way I stated above).

What you say?

 

[Rukbat]

The battery won't go from working fully to fully dead in one day,. but buying a battery now and letting it sit on the shelf for 2 years could leave you with a dead (and nonchargeable) spare battery. Wait until it shows signs of getting old (like taking longer or shorter to charge or lasting for less time between needing charging). To preserve it even longer though, don't charge to more than 70% and don't drop it to lower than 30% (40% minimum is even better).

If you're running Magisk (or thinking of rooting), running Magisk Charging Switch, a Magisk module, will pretty much force you into good habits. Setting it to 70 30 will stop the charging at 70%, and it won't start charging again until it drops to 30%, even with the charger plugged in.