This is mainly aimed at those with E series firmware who still have issues., but it is applicable to all variants and realistically, any Android device.
I haven't had the issues others have been experiencing, in fact despite heavy use my device had been working brilliantly and have been using it fairly heavily.
I know that most problems my friends have had is the direct result of apps loading into the memory at boot, including games just to push ads. This includes device freezes and reboots. Sometimes these were caused by something seemingly unrelated, like an app (that's not being used) pushing an ad whilst using gps. I'm fine when the app is in use, but I think Google shouldn't allow most apps and games to do this. Their solution is adaptive battery in Android 9? Not useful if you keep the phone clean. Having them permanently in the memory means you're susceptible to any bugs they have, and potentially any security issues they have. Also most aren't exactly programmed well.