That depends, if you buy a flagship device then in 5 years it will probably still be quite usable, but the battery could already be shot.
My phone (not even a flagship model) is coming up on 4 years old and it’s still pretty fast and on the newest Android version (yay custom ROMs), but the battery now struggles to get me through a regular day, so it will probably need to be replaced soon.
I’m currently using a Mi Band 6 (with a nylon strap that’s real comfy), but I wish the Pebble still existed. The e-paper display, the nice UI and tactile buttons, with good battery life and the ability to make apps was great.
Once my Mi Band breaks, I’m torn between Garmin (since they check almost all of the Pebble boxes, even if I don’t do fitness and they’re more fitness oriented) and a Galaxy Watch with the rotating bezel, since that was really cool to play with, plus the Android integration might be nicer.