I don't think you're ever too old to wear any kind of underwear. And if you want to tell you're girlfriend then go ahead but honestly, I don't think it's that big a deal.
Actually, briefs can cause infertility in men(but thats only if you were them up in your twenties, and longer) but nah they wont hurt you, but boxers are much more comfortable.... much more manuverability. But if you like the support of briefs wear e...
From a health standpoint, boxers are better as they "let the boys breathe" easier. Briefs aren't too bad as long as they're not too tight. Bikini briefs squeeze too much and push everything too tight to the body (not good).