Best to assume the following about stated ages unless there is clear evidence otherwise:
18.......Not yet 40.
29.......Wrong side of 40 but don't yet need a zimmer frame to get around.
"Mature".....everything else <shudder>. If you like GGGGGGGGGGGGGGGGGGGGGILFs this is for you
If I'm lying, then how come a girl I first saw 3 years ago was "29" at the time, and is now "27"?
Perhaps Douglas Adams' 6th book in the Hitchhiker trilogy would have touched on prossiemathics.