Is this true?

Is it true the longer a couple stays together (cohabitate), the chance them getting married becomes more unlikely? I personally think that the only difference is a technicality and after 8 years it doesn't even matter. However, I do think I am being cheated out of explanation at least because most of the time I don't know what to think on the subject since I don't know what his stance is or about any marriage plans he may or may not have. I mean damn shouldn't I be able to decide what I am cool with?