Well, I am 25 and have been a Console and now PC gamer since well Sega Master System. It has been one of my go to hobbies for many years and owning an expensive PC has also brought me hundreds of hours of enjoyment. Not that it's all I do.
But for the most part I can't play single player games for any long period of time. Hell even when I do I am usually on Mumble chatting etc
Simply because I enjoy the MP aspect, just broke 800 hours in Battlefield 3. And some of the most fun times have been with friends. Hell whether we are winning or loosing still fun.
I don't think I will ever grow out of games, ask MarkCUK he's in his forties I think, and his son Dannyman191 also game with us.