Should I let my daughter (18) stay the night at her boyfriends house (18) (His parents are at the house as well along with siblings)?

My daughter (18F) has been with her boyfriend (18F) for over 2 years. She is in college and her boyfriend is halfway through his senior year. My curfew for her is 9 on a weeknight and 10/11 on the weekend (depending on how I feel). She has been coming home later each time looking sleepy and says they fell asleep at his house and then is grumpy when she arrives home. Should I start letting her stay the night at his house? His parents have both stated they are comfortable with her staying the night at their house until he’s graduated high school, then they said they’ll let him stay the night at her college (2:30 hours away). Every time she comes home, she is later than the previous night and I don’t know what to do. She’s currently on Winter break from college. Should I start letting her stay the night with him?