I just turned 30 and I feel like I'm kinda at the point where I won't wear one unless I'm actually going to the game, or to hang out at a sports bar on gameday. I used to wear them on random days, but not anymore. Don't know why. Just don't.
I used to wear the in Junior High. But these days if you see a grown man wearing a jersey. It's a sure fire way to spot an ignorant idiot.