Chronologically, late 40's. I look 30 and nobody ever believes I'm as old as I am. My bones know their age, though, especially after a fall (pretty common for me) or before it rains.
I don't keep close RL friends, but have a pretty steady group of kids 8-13 that I play pokemon and mess with robots with. We get pretty silly and I have a great time. I am really concious of our age difference, because I have to be. Since I have (adult) sons of my own, most of the parents are ok with me (some are jealous because I get along with their kids so well), but most of them think I'm harmless and weird.
I have a lot of acquaintences from dog training. They are fun to be with because most of them are goal oriented and want to train and talk about training. I have a rough time of it when they start talking about "adult social stuff" because then I get deadly bored and just wander off. Not good for making connections...
The guys at work are the best, and are learning to understand me, so they give me about the right amount of "society". They are all young enough to be my kids (but I don't look or act like their mothers!) so they don't expect anything social from me "after hours".
I mostly prefer kids and preteens because they haven't learned not to invest themselves wholly in whatever is interesting and fun.
I hate worse than anything to be "trapped" with boring people (which means almost everyone). I think that's what I dread most about social stuff, parties and cocktail hours, and stuff. Most people are just not able to talk about real things, or are not interested in what I am, or able to just SHUT UP and watch the wind in the trees or water or whatever and physically experience stuff without yapping about b*llsh*t.
With many kids on the other hand, we can have a lovely time digging holes and watching them fill with water, hunting for snakes and bugs, or whatever.