I know they say "There are no stupid questions" but I may put the lie to that adage today. Do picks wear out? and if so, how do you know when to change them?
Yes they wear out. When I am off to a week at Ashokan "Western and Swing Week" I will go through 2 maybe 3 in one week. For me they crack and break so it's easy to tell when to change. I like Fender medium. Also I keep a small piece of 400 grit sandpaper in my pickbox to smooth off the rough edges when they get rough or too sharp. I am sure they are picks that don't wear or break as much but I use what I like and they are cheap enough.