It of course depends on a lot of factors, but a number of Android devices have performance degradation over time, so it can't always be blamed on app upgrades.

It of course depends on a lot of factors, but a number of Android devices have performance degradation over time, so it can't always be blamed on app upgrades. See for example: https://play.google.com/store/apps/details?id=com.grilledmonkey.lagfix https://play.google.com/store/apps/details?id=com.grilledmon... and googling whatever specific device you have for the thousands of other people with the same problem.