I’ve had my Steam Deck for about two years now, I thought I’d share two recent wear-and-tear notes…
At the start of this year, my left joystick started having issues in the southeast quadrant. They started with some drift-like behavior, then an audible “click” when moving in that direction. Searching for the problem online, most said it was an issue with newer joysticks and would improve with use. Even though mine is two years old, that advice seemed accurate… the problem improved on its own, and now seems to have gone away. No idea. 
I’ve been using the official case this whole time. Last week the zipper started to separate from the seam at the far edge, making it harder to close. So I bought one of the cases that I’ve seen @BMO recommend a few times, and I honestly wish I’d done so a lot sooner. I expected it to be much lower profile (it is), but I was surprised by how much lighter it feels to carry, too.