Well, I'm openly bisexual and 32, been out since I was 20. A lot of my male and female friends are bi, and we've got a few gay/lesbian crew as well. When I was younger I was heavily involved in the gay rights campaigns and organising of Pride festivals and so on (more of a celebratory party here these days than a political demonstration and folk are pretty gay-friendly over here, at least in the big cities).
Having said that, I'm very happily married and would never ever break my marriage vows. Does that still make me bi? I don't know. I'm still attracted to some guys, would still masturbate to some gay porn. But every single gay and straight guy/girl I've ever been in a relationship with has always gone 'but won't you get tired of just being with one type, not being able to have gay sex in my straight marriage, or not being able to fondle breasts in my prior gay relationships (surprisingly, I don't go for androgeny - I like my women curvy and busty, and I like my guys lean but well-toned, and a thin bit of facial hair is awesome). They don't get that the whole point of being bi is that you simply don't switch on to those kind of things - it isn't like 'oh, I've had sex with guys for ages, now I want a girl' or vice versa'. It's 'here's a person I'm attracted to and really really care about and I could care less what gender he/she is, and never will.