Ah, the age-old friends with benefits situation. However, friends with benefits also come with a few asterisks.
Both of you need to be on the same page in case either of you start developing feelings for each other. Same thing goes if one person wants to end it. You both have to be okay with the end result.
The main point of having a FWB is to have amazing, satisfying sex. Having casual sex can be emotionally tough, for some more than others.
Having sleepovers confuses things. You want to keep yourself from getting emotionally attached, so sleeping next to your FWB—and walking up next to them—is extremely intimate. Say goodnight, take a shower, and get into bed feeling relaxed, satisfied, and totally comfortable with the fact that they went home. Cuddling encourages intimacy which is a no-no with a friend with benefits. You want to keep things simple. This is a friendship, not a relationship. Leaving a change of clothes or toothbrush at their place is highly discouraged, as is giving them grief if they have plans, a date, or have to cancel on you.
Once you become a stage 5 clinger, the fun is done.