I use a Progressive Web App on a Samsung Galaxy S3 smartphone (1GB RAM) on a regular basis. If the phone just got a fresh ROM, rebooted within the last hour and

I use a Progressive Web App on a Samsung Galaxy S3 smartphone (1GB RAM) on a regular basis. If the phone just got a fresh ROM, rebooted within the last hour and the app is a fresh installation, I have no performance issues what-so-ever (~60 FPS animations, etc.). But over time things degrade. I don't know why, but every year or so I have to format the internal SD card to keep the OS in shape. If I install too many apps which run in the background the RAM gets crowded and everything starts lagging. And finally, the app itself is not as optimized as it should be, so that when I use it with the data I enter during a year or so, there are some steps which take a few seconds (rendering a list with >300 items/DOM nodes). By the way, a 'couple of seconds' is unacceptable from a UX perspective. So this is just one example where you can have a 100% good experience but also a very degraded experience with the same hardware and software, due to different factors (from OS degradation to awful O(n) optimization).