Oh, it's no problem at all, it's just something very involved which would have gone very off topic for me to try to answer it in that thread.
To answer the questions you've asked, we've been together nearly four years now, we've been living together slightly over a year and a half, and we managed to work out the quirks and complications of our arrangement pretty early on (with a good deal of helpful advice from a couple friends we made, who're involved in stable poly relationships themselves.)
We met in college, during work for Habitat for Humanity with a student group, and at first just immediately clicked with each other and got to be very close friends. That evolved over a few months into being something other than us simply being friends, though that is highly understating the complexity of it all. We are what some people call "accidentally poly," because we didn't not set out to form a poly relationship, it just "happened." After a lot of emotional, romantic, interpersonal and sexual "fumbling around" (again, with some very good advice we still owe certain friends greatly for) we came to the conclusion that it was going to be workable.. and it has been since. Our last major "hurdle" was cohabitation, but after some "shit just got very real" moments that's turned out to have been a lot easier than any of us thought it would be. (Not to mention being absurdly financially and practically advantageous, though we didn't realize at first how much so that would be.)
This is probably going to sound very odd to you, but ours is a mixed-orientation relationship, and it's not a sexual "triangle." I have a girlfriend and a co-boyfriend, and only my girlfriend is a sexual partner for me. My co-boyfriend and girlfriend are both straight, though friends who've found out that we're poly usually at first assume that he might also be bi, because I am. (He's actually not bothered by that, and finds it amusing when it happens.) That does not mean that he's any less important to me than she is, or vice versa, just not in the same way. "Co-boyfriend" (or "co-husband," in extralegal group marriages) is a relationship type which is difficult to explain, because people who haven't been involved in the sort of relationship situation where that comes about literally have no common frame of reference to use to understand it.
Our relationship is also polyfidelitous, meaning that we do not have outside partners. Yes, this does mean I haven't had a male sexual partner since my second year of college. At first both he and her suggested that it wouldn't be "unfair" for me to be a bit "recreational" occasionally, but I rejected that idea. Like a lot of people, they did not at first completely understand that being bisexual doesn't mean you need to have sex or relationships with people of both genders, it just means I'm capable of either. I do occasionally miss sexual "guy time" a bit, but I have my harmless outlets (which they're perfectly fine with) when I have the very occasional pang over that. Neither of my partners are prudes.
Many people we know actually aren't aware that we're poly, as "coming out of the poly closet" isn't a common thing. Particularly when it comes to closed poly relationships, those involved have absolutely no practical reason to let others even know what they're "doing," and wouldn't want to invite outside interest by doing so anyway. This leads to people thinking of closed poly relationships being rare, and for a lot of people thinking poly on the whole is a lot less common than it is. If you're involved in a local poly "tribe," you end up meeting people you'd never expect it of. Admittedly, most are at least a bit older than us. There's another closed triad we're good friends with, who're in their mid 30's and early 40's, and they consider us sort of "adorable" because of our ages.
Friends who we decide to invite into our home are informed, after we decide whether they can handle it or not, because this is our "safe space" where we feel totally free to interact without having to worry about what others might think. Most other people just believe it's a roommate situation involving a couple and a mutual friend. We're fairly careful about it, and have had only one serious mishap (involving a former gay friend of ours who seemed alright with it in theory, but couldn't handle the reality of it.)
Her parents know, and have met me and him (they do not much like us, but are grudgingly tolerant because there's nothing they can do about it.) His parents are neo-hippies (a fact he finds just slightly embarrassing) and practically dote on us. My co-boyfriend's mother is also bisexual, but is happily and monogamously married, and they're about most shockingly happy couple I've ever run into (though they're a bit eccentric, but not un-charmingly so.) My folks have met her, but I haven't figured out the best way of explaining the full situation to them without distressing them. (They're liberal, but they're not that liberal.) My folks and brother are aware that I'm bi, and have known that since not too long after I figured it out, but poly is a very different subject.
I think that covers everything you've asked. Like I said, I don't mind people being curious about us, except when it comes to specific bedroom situations (but the general subject doesn't bother us.) Most people in poly relationships are very cagey and defensive about it, but we do make a point of not acting like that, because it really does foster a lot of misunderstandings about it. Anything else you might be curious about, feel free to ask, you won't offend us unless you actively try to. :)
If you're looking for alternate viewpoints on this, flux365 is also poly and a pretty friendly guy. His relationships have been rather different than ours though, being that they've been open and (to the best of my knowledge) not mixed-gender.