Oooh, good one. You really got me there.
I figure once you reached the point in a relationship where the two of you are trying to figure out how you’re going to pay for both the mortgage and your kid’s college tuition, you’ve moved past the boyfriend/girlfriend stage.
No apologies needed. 
And yep, the 'Dope is very US centric (and completely understandably so), but I like the place… even if most of you are Americans. 
(Seriously though, I’ve very much enjoyed the various times I’ve got to spend in the US, met a lot of very nice people, and would really enjoy going back… perhaps once you’ve reined in the TSA).
I wouldn’t jump to the conclusion that partner referred to same-sex partner, since I’ve often come across people from various British Commonwealth countries who referred to their opposite-sex love interest that way. (Disclaimer: I’m not American.)
I just don’t know anymore.
I used to act in a small theatre group, and by crikey there are a lot of gay people who involve themselves in theatre. I wonder what’s up with that.
Anyways, when I was about 22 years old, I heard one of the actors refer to his partner as his Husband. And my immediate reaction to that was confusion. For one thing, I didn’t pick him specifically as being gay, so it was a surprise to me anyway. But also, I’d never heard the term used that way before then, and in fact I’ve barely heard it since.
So at first I thought it was the wrong word to use, it just felt like it was reserved for heterosexual relationships. But since then I have pondered my kneejerk reaction a lot, and have decided that it is not only an appropriate term, but probably the only correct one, assuming they got legally married someplace.
Even though I, like the OP, immediately jump to a “same sex relationship” conclusion when I hear a non-gender-specific term like “partner,” I also immediately suppress my baseless assumption, filing it away until more information comes to light. Which only happens rarely.
That’s what I do. But that doesn’t make it any less annoying.
It appears that I must take a moment and straighten all of this out for the world.
For legally unmarried folks under the age of 40, the following applies:
Boyfriend/girlfriend regardless of any condition other than not legally married…unless they have had a legal partnership or personal long term commitment, in which case the terms life friend will suffice in all cases regardless of gender of the principle parties.
For legally unmarried folks 40 and over in age, the following applies:
Manfriend/Womanfriend regardless of any condition other than not legally married…unless they have had a legal partnership or personal long term commitment, in which case the terms boytoy or womantoy will be applied - regardless of the gender of the principle parties.
If the parties are traditionally legally married they can be called the Mister and Missus. Only Old Man and Old Lady are forever banned for all humans. Certain white haired cacti are allowed to use these names.
All third parties to these pairings shall be referred to as “Squeeze” as in “Secondary Squeeze”, or “Squeeze on my wallet”
Remember, folks, I’m just kidding. Everyone should call their relationship and partners however they wish, just remembering that if you use the term marriage, you should be married regardless of genders. All combinations OK.
Woohoo! I get to have a boytoy next year! Excellent!
Hang on, I’m under 40, but the guy I’ve been living with for 17 years, and have two kids and a mortgage with, and who I wouldn’t marry even if he asked me, which he wouldn’t, is over 40. So do I have a boyfriend or a manfriend (that just sounds ridiculous) and does he have a girlfriend or a womanfriend? And if he isnt my partner, what is he?
The English language seriously needs a simple, informal single word for live-in B/GF. In the Scandinavian languages we have a word like that, probably because cohabitation without marriage is generally accepted (living together for more than twenty years without marriage is not directly uncommon), and living together for an indefinite period of time before marrying - the marriage often happens when the hetero couple has started thinking seriously about having children - is the norm unless you belong to a very religious society.
Because of this, the word for live-in B/GF is very common and non-sexual-orientation-specific (however, since the word itself doesn’t contain any direct references to a romantic relationship, it’s sometimes used jokingly about a roommate), while “partner” is gay-specific since gay partnership was the norm before SSM was allowed. Now that also SSM is allowed, the term wife/husband is used by both gays and straights.
ETA: Gay people actually started using wife or husband about their registered partner even before SSM was sanctioned. I guess it was meant as a political statement.
All I know is that my response to lindsaybluth’s uncle would be to refer to him and his partner as queer-fag-buttmonkeys. If he doesn’t care that he’s calling people something that is offensive tot them, why should I care about him?
Okay, I probably would try a nicer approach. But, geez, what bigotry.
So what? Wouldn’t both alternatives place the woman outside the pool of desired dates? 
Me and my “partner” would like to offer you the opportunity to have your trees trimmed and everything put on our trailer and removed for “x”- $. Am I gay?
I wouldn’t know, but if I were inviting you and your partner for a dinner in my house, you’d probably be gay.
It’s usually a matter of context 
Off the top of my head I don’t know anyone (gay, straight or bi) that doesn’t call their unmarried partner…well, their partner. Most people I know wouldn’t say “my boyfriend/my girlfriend” unless they were trying to be cute.
I think I failed to explain myself perfectly there. I am not saying that the legal rights and so forth of our present legal marriages should be subject to anyone’s individual interpretation. Quite the contrary–our current problem is that the law is subservient to a biased cultural tradition which says that this person and that may “marry,” but this one and that one may not. The grip of this tradition on the law has been eased in parts here and there, but I wish to see it broken entirely.
The package of legal rights and responsibilities which has been gathered under an extralegal (largely but not entirely religious) concept should be (a) renamed something other than “marriage,” to free it from the cultural baggage, and (b) made available equally under the law to all sets of adults who wish to avail themselves of and bind themselves by it, just as other kinds of legal contracts and constructs are available.
In other words, it’s not properly the government’s business who makes a “civil union” or “domestic partnership,” or why, any more than it is the government’s business who forms a “limited liability corporation”–but the legal meanings of each construct, once made, should be equally and impartially enforceable.
Then, with the word “marriage” no longer tied to the law, people can do what they wish with it. If the Church of ABC wants to say that only marriages between one white man and one white woman are acceptable and valid in the eyes of God, let them have the free exercise of this religious belief. They can perform their own marriages as private ceremonies, and they can talk all they want about how all the others are false and sinful. At the same time the XYZ Coven can be conducting marriages for lesbian triads, or whatever the hell they want to do. Everybody can do what they like, for themselves only. Nobody may impose their religious or personal belief system.
The law itself should be impartial. It isn’t now.
You could call him “my man.”
But “partner” seems to me to work pretty well. It includes connotations of companionship and working-together and loyalty. I find it mature and even elegant.
I use “partner” for the same reason I use the title “Ms”: My marital status isn’t anyone else’s business unless I specifically want to share that information.
You could always do what my boss at my first post-college job did when introducing me to his S.O. at a party; “Hello, I’d like you to meet my lover, Taffy.” (Taffy was a dentist. I swear, the whole scene was straight out of a sitcom.) I was new to workplace etiquette issues, and really didn’t know what to say because I was too busy clearing images of the two people in front of me having sex out of my brain.
A “lover” is fantastically stylish, but of course not carrying the same connotations as a “partner.”