Why not bring this into your relationship? Think about it - who better to spend a evening staying up late with than your partner? Set it up with snacks and fun things to do. Some fun things you can do are play twister (that could get some giggles) or bring your laptop into your bed and watch a movie or some funny video clips on YouTube. You could play a game or ask each other deep and meaningful questions late into the night.
Just have fun together and enjoy that wonderful relationships can have the element of friendship in them, too.