These days, with the internet being a big factor of success, and that there is a certain degree of anonymity to that, I'd say age doesn't have such a big factor these days. Also, Grant Kirkhope was in his 30s when he was recruited to Rare. Its easy to put yourself down by saying "oh i'm 15/23/35, I should have become famous by now" or something along those lines, but if you want to truly become good and notable for something, it takes hard work, dedication, time, and honestly, a degree of maturity that comes with age. I wouldn't think there is anything to worry about.