boots... I guess it depends how much you ski. I wore a pair a bit too long, and they actually sheered mid turn at the ankle. Top separated from the bottom. Been skiing a long time so wasn't a problem but yeah do keep checking them and don't assume they will last forever!
My rule of thumb is new boots roughly every 90->120 days of skiing new boot time. For me that's normally every 3 years (but not recently due to covid)