I own both a 801 device (LG G3) and a 810 (Sony Z4). The 801 runs way hotter than 810 with frequent throttling. There are times I have to stop playing a game because my fingers are burning! At XDA you will even find hardware mods for cooling the CPU. :)
Unfortunately this is the only way for Android team to enforce good practices to most manufacturers. If not, you would still see new devices coming out without usable encryption support. The older handsets will still be protected by Play Services as long as they stay mostly in Play Store and don't install random apks from the net.
Yes, planned obsolescence is an issue, especially for countries or groups with lower income. On the other hand phones get such an abuse through daily use that few of them last for 3 or more years.