I'll be 38 just before Christmas this year, and except for minor seasonal/motivational breaks over the years, I've been at it since about age 7.
My mom and one older brother got me into it way back when, and both are still enthusiastic; he still builds on rare occasions, but she has yet to get back at it(she has a stash of 5 or 6 unbuilts & about 5 built-ups). My wife is a scrapbooker, so neither of us can throw stones about how much space and $$ each other's hobbies consume....I got her into building a few years back, and she has one finished model - with about 4 more waiting for attention.