I missed this before, but one of my current instructors started at 28, and another (this guy:
http://www.sherdog.com/fightfinder/f...FighterID=8092) at 26. The one that started later hasn't fought pro, but has won a lot of amatuer tourneys and is still competing now at 41.
I've had students variously neck crank me into job loss, heel hook me tearing every tendon and ligament from the knee down on my right leg, try to touch my hand to the back of my head with a kimura, armbar me at 100% intensity while ignoring my tapping until I screamed, sucker punch me in the middle of instructing, knee me in the balls during a drill (intentionally), and go for an ear grind when my cauliflower was already 1" thick. Be glad you're only a student.