Since this has turned into more of a 'share your age' thread, I'm 40 -- been playing DOOM since maybe about 1996? (It was the PlayStation 1 version, in Europe; that year feels kinda right somehow) and mapping since 1999; late to the party at the time, I had no idea the scene would endure as much as it has! Indeed, when I joined this forum in my twenties way back when, I felt like one of the inexperienced kids on the block! (Still do, kinda, which is weird)
Also, as an aside, I literally saw the millennium in playing DOOM. Nice.