It's as easy to ruin a relationship by jumping in head-first as by backing off -- it's perhaps even easier, since the number of things that can go wrong in a joint living situation is pretty infinite. To avoid unforeseen conflicts, you might want to consider:
One of the biggest relationship stressors (much bigger than a beach vacation) is money. Moving in together means tying your lives together financially, and if you don't know what you're getting into, you could end up with more conflict (not to mention resentment) than you bargained for. Is your partner a spender? A saver? A starving artist? A compulsive shopper? It doesn't necessarily matter what the answers are, you just need to have them before you commit to cohabitation so you can make an informed decision before jumping in.
So, you already spend five nights a week at your partner's place. The question is, do you count the hours until you get to go home and be alone? Living together part-time is very different from really living together. Are you ready to give up a lot of your personal space and privacy? And are you and your partner on the same page regarding how much of that space and privacy you'll maintain after merging homes?
Moving in together can be a smart thing for couples who are already spending most of their time together. You'll both cut your living expenses, and you'll be burning a lot less gas when you don't have to drive back and forth from each other's homes.
And if one of you thinks you're being smart by moving in together, and the other thinks you're preparing to get married, someone is going to end up very hurt (and/or homeless). Motivations are a crucial factor and need to be understood beforehand.
Another point about motivations: If you're moving in with your partner mostly because you feel pressured to do so, reconsider. Success in sharing a home requires two very willing participants. Going in half-hearted practically guarantees you won't be able to put in the effort to make it work.
If you or your partner has children, the ante is significantly upped. Moving in and moving out is a much bigger deal when there are children moving with you, so think about it long and hard, and then think about it again. Most kids need stability to thrive.
And if you think about it, and think about it again, and you still want to share a home with the one you love, consider a few tips for a successful union…