staying at boyfriends

Hi! Im 19 and know i dont necessarily need permission but they will know. I come home next week fromcollege and want to stay at my bfs college house for a night. I was going to say that theres a date night party and he invited me. Its a 2 hr drive so i wouldnt want to drive home at night. Does anyone have any ideas on how to convince them. I have tests this week and was hoping if i did good they would consider it even more. Advice? We've been together 2 years... i know this wont make parents say yes but at college i can have any guy/ multiple people sleep with me and they will never know. Ive been with him for awhile and they love him. Any ideas?