I'm all for monogamy, but not so sure about an actual marriage. I've never cheated on someone I was seriously involved with so needing the legal ceremony isn't necessary, IMHO. If you plan on having kids, I'm old fashioned enough to think you should be married at least when they're born, but for old folks like me, there doesn't seem to be a point in getting a document that legally and emotionally is sometimes not worth the paper it's printed on.
I loved being married, but I hated going through the divorce and I'm still gun shy after 20 years.
Then again, I might meet someone tomorrow and be married by Sunday.