I'm using my Samsung Galaxy S8 for now 2 years and I have to format it in every 6 months because it starts crashing apps and slows down so much that I don't have any other choice but to format it. but now formatting it not a solution because in next 5 days it again slows down this makes me unwillingly upgrade my phone, in this case, I think Apple does a better job as there customer know what to do to get that Phone speed back!
i too have an s8 for 1.5 years and my usage is 8 hour day yeah there is heating problem in summers and battery is not that great but i never faces slowing down type problems
i always disabled or uninstall unnecessary apps and restarts every week
