I play a lot of fantasy monster characters who run 200-2k years old. In fact, most of the characters I am currently playing are at least 100 years old. 

When playing boring humans I usually pick early to mid-thirties. Maybe forties. I rarely ever play anyone younger than 25 and I never play children unless they are NPC/side-characters who don't interact with the main characters much at all. Most of my RPs have mature themes and I have a strict "no pedo" rule that includes RP partners who are under 18 (sorry, kids.)