I had my son (DYS) at 24...so can't say advanced age had anything to do with his gifted levels. I had our twins at 27 and they are bright as well (age 5), but haven't been tested as we finally saved to afford for our oldest to test this past summer.

My DH is exceptionally bright and his mother and father were 17 when he was born...

I agree with several posters who said that its likely more children whose parents are in the advanced ages are identified as gifted because they tend to be more educated, with better paying jobs, leading to be able to afford testing and search out more than those with less education.