As @ttf says, a lot of phones will be close to unsuable by the end of 2 years. I think part of it is simply that faster phones means all the apps get more complex and run slower on your phone, but also those components simply warp and degrade with all the heat generated by the work they are doing 24/7.
So, yeah 2-3 years is about normal I reckon. It’s not really great but that’s how it is. I’m pretty lucky that my OnePlus 3 has been going for 3 years now and so far has given me no reason to upgrade.