No, after the warranty runs out the max brightness stays the same. It's just that if it burns one day after the warranty, your SOL. What's so hard to understand?
Samsung all they care about is making a phone that will knock your socks off with the best display on the market to buy it and that they set their tolerances on their phones best they can to make sure it lasts throughout the warranty period so that they don't lose money having to fix/replace parts.
It's not neglect if a user wants to max out their display... the person could have bad eyes and need a phone at max bright... Samsung set the max bright and auto bright so should be no issue. But yeah a user should maybe know that doesn't help in longevity maybe... that after the warranty he keeps doing it, you're increasing the chance of accelerated wear.
But you spend 1K on a phone and it burns in months because you want to set it bright? Come on.
Oh I understand I was kinda being sarcastic in my first statement. You said "Samsung sets the max brightness level so they do it within tolerances of the screen they feel it can handle at least during the warranty period" which makes it sound like it was just during the warranty period they set those tolerances for. But yeah if it's something odd like the OP stated then I can see that being an issue. Like I said if someone wants to use max brightness and keep the screen on for long periods of time then go for it just know that it increases the chance for burn in and decreases the displays longevity.