You get to spend time together: When you move in together, you get to spend more time with your partner. This helps you be with your partner for more time even after having a hectic schedule.
Happy sex lives: Sex is obvious as you two will stay together in the same house! You get to spend more time on bed together. Instead of meeting once or twice a week, you have whole night to try new positions and tricks.
You can re-think: Well, one of the best thing about friends with benefits relationship is, there is no commitment. You two stay together till you two want to! This mutual understanding helps you have a healthy relationship with your partner.
Restricting to one: Even after no commitment, you two are bound to stay together. Once you move in with your partner, leaving the house can be tricky. You will be restricted to only one partner even after being in an open relationship.
Difficult to get others in bedroom: Well it is not a commitment. It is an open relationship where you mutually stay together till you want to. Although you are with one partner, you cannot get another new partner to have fun. What if you find a hot chick in the party and wish to get her home? You will obviously feel awkward to enter with some other girl when one is already waiting for you inside.
Boredom: An active sex life becomes boring after few weeks or months. You can try several varieties but, maintaining the interest of a man in you is very difficult. This is more common in such relationship where you are only with each other for mutual benefits especially sex!
Friends with benefits is a rising trend among youngsters. However, moving in with such a complicated relationship can be troublesome at both the ends.