If you are in a long-term relationship, you are going to get to the point where you decide to move in together. Whether it be temporary, as my situation was, or permanent, just know something: it's different.
When you decide to have a significant other move in you probably aren't expecting it to be much different from living with one of your best friend's. The one huge difference between living with your besties versus living with your partner is that it could become permanent.
Most likely, you aren't going to live with your three roommates for the rest of your life; however, if things go well and your relationship takes you all the way down the aisle, you'll be living with that person for the rest of your life. Living with your boyfriend or girlfriend is an incredible experience, one that I recommend long-term couples try.
It's more than just learning whether or not you are compatible to live together, it's about learning if you're compatible enough to be together.
I found that my boyfriend does little things around the house that drive me crazy in my head. I asked him and he said the same for me. Yet, neither of us expressed any annoyance, issues, or unhappiness from living together. It's different than just visiting their house and sleeping over because that isn't your space.
It's easy to say "my boyfriend's place is messy" or "my girlfriend always leaves her shoes everywhere" and not be bothered by it when you aren't sharing the space. Once you move in together, the things they do that bother you the most become really obvious. You can't just invite them to your place or overlook the problem when you sleepover, you have to communicate and figure out how to make it work for the both of you.
For example, my boyfriend has a notoriously messy room at his place and an ugly pig's head that (this is a real shocker) someone randomly gave him for free. I hate mess and I hate that someone would own a pig's head. When he moved in here, I could tell that he made an effort to keep any of his mess in his own space and be extra clean for me (he also left the pig head at home, thank goodness).
When you love someone, you adjust! It's not about changing the way that you live or like to live in spite of someone, it's changing the way you live because you want to love living with that person.
Living together can make you more appreciative of your significant other and really make the little things they do for you stand out. When you live with another person, you get to the point where you overlook things that would bother you regularly.
Moving in together can help your relationship mature and your understanding and love for each other will blossom in new ways.