Euphemisms for "Living in Sin"

Times have changed.  Whereas back in 1960 or so, less than 10 percent of subsequently married couples lived together before marriage, nowadays about 60 percent do so.  And, of course, there are those who live together for a while, but who never get married.  One of the factors is that both men and women get married somewhat older nowadays: 27 for men and 26 for women; as opposed to 23 for men and 20 for women back in 1960.

And in some settings or communities, this is more common than in others.  For example, in Atlanta 22 percent of couples were living together but unmarried according to the 2000 census.  It's much lower in Salt Lake City or El Paso.  This change in couple demographics has required some families and groups to make accommodations.  Or, in the case of where traditional values linger, some subterfuge.  [Schoolteachers living together without marriage usually are at risk of termination or not having their contracts renewed.]  

But there is the linguistic accommodation.  How do you refer to people living in this sort of state?  Here's a few, with some commentary:

1.  Shacking up -- Somewhat 1940's in use; also carries disrespect for the habitation shared by the couple.

2.  Significant other -- This must have been coined by a lawyer.

3.  Lover -- To the point in a way; but can't married couples also be lovers?  And what about Platonic lovers?

4.  Main squeeze -- Somehow, juice imagery comes to mind.

5.  Common-law spouse -- An old term.

6.  Old lady or old man -- Only for motorcyclists.  But teens sometimes refer to their parents in such a way.  Not a wise move for family harmony.

7.  Cohabitor -- Too pointed and clinical.  You may as well refer to "the person I have coitus with."

8.  Companion -- Only if she or he is a real dog [slang!].

9.  Living in Sin -- Can either imply a moral judgment, or an ironic commentary on the state of living together with benefits.*

10.  Friend with Benefits -- This euphemism implies that they're having sex; but FWBs don't have to live together.

11.  Persons of Opposite Sexes Sharing Living Quarters (POSSLQ) -- I swear, the U.S. Census came up with a neutral term to describe this shared nonmarital state.  In response to this term, CBS's Charles Osgood wrote this tender romantic poem:

There's nothing that I wouldn't do

If you would be my POSSLQ

You live with me and I with you,

And you will be my POSSLQ.

I'll be your friend and so much more;

That's what a POSSLQ is for

12.  Domestic partner -- Very commonly used, but quite oblique.

13.  Trial marriage partner -- It's like the person is saying, "I'm taking him for a test drive to see if he steers well and doesn't leak."

14.  Friend -- Too vague.

15.  Sex partner or the like -- Emphasis on only one aspect of the arrangement.

16.  In a relationship -- Keeps it satisfyingly vague.  

17.  Plays house together -- Too cute.

Obviously, the terminology adopted by the person carries heavily what he or she thinks or feels about what is going on.  Have you any other suggestions to cope with this linguistic terminology gap currently facing users of American English users?

*I was NOT implying disapproval of this; quite the contrary.

Let not the cohabitation of true minds admit impediments