I've been ID'd less and less. Maybe 25% of the time I'm ID'd now. I'm 28.
One of my favorite non-ID'd moments came this week. I did a 5K mud run (so fun) and there were free beer tickets we got when we signed up. I walked up to this counter to get my beer, and a woman (who I think was older than me) seemed upset that she was being carded. I walked up, handed my free beer ticket to the guy and he gave me a beer and as I was walking away, the woman gave the guy a major WTF look with a gasp. I almost busted up laughing.
I'm an on-time college student, so I get carded unless it's a really small store and the cashier doesn't care at all. I usually think that I look 22, but there have been occasions when I've stated that I'm 18 and people believe me.