I would prefer 13+, since I get tired of more immature members on the Forums and in-game.
But, then I think back 5~ years ago and realise I was just turned 13 when I joined, and I was immature too. There are old posts of mine that I cringe about. And I made a fool of myself in front of members who I now know better, and I question if they remember my stupidity.
I'm happy for all ages to be here. Everyone deserves a chance. Some waste theirs, but that's the fault of their character, not their age.
And I have no problem with older members. I'll be 18 this Summer, myself, and I'll likely still be popping on here still. Older members have just as much chance of being compelte richard heads as any younger members too.
There might be some correlation between age and maturity, but it's not set in stone. There will be perfectly good members who are young (A number of members I've come to like and respect turned out to be rather young, to my surprise) and there will be older members who are wastes of space.
I can't limit one age-group to being present here, since I'll be kicking out good and bad people whichever way I choose.