What about those of us who don’t want marriage, but still want a long term relationship?

Is there ever a time when you stop testing their value? I have zero interest in getting married, and in what I’ve been reading so far, that seems like a common moment when they’re accepted a bit more for their true value. I know I will never again put myself in a position to rely on anyone, but what’s the difference between a forever girlfriend and a woman who isn’t interested in getting married? What are the lines we draw to benefit the most without actually legally attaching ourselves to someone?