My boyfriend moved into my house with me about a year ago, and for about 9 months we were sleeping in the same bed (the master bedroom). There is a similarly-sized guest bedroom that also has a double bed in it, however, and he started sleeping in that every now and then because I had a personal fan I used to run on my bedside table that he said was too noisy and stopped him getting to sleep.
So I stopped turning the fan on and now the room is pretty quiet, but almost every night now he starts in bed with me, and then after maybe 30 minutes gets up and goes to sleep in the other bed. He says that room is better for him because it's a bit darker and the bed is warmer (thicker duvet), but I prefer the conditions of the master bedroom and it's a perfectly good bed. The guest bedroom would make it harder for me to sleep because I would find it too hot. He's also saying he needs "white noise" which would probably disturb my sleep. I'm sure he can sleep in the master bedroom because he has done so for about 9 months until he started changing beds.
I've told him this is making me unhappy and that I want us to sleep in the same bed, and the response is basically "well, make the master bedroom more like this one because I can't sleep properly in that bed", but I don't like sleeping in the conditions of the other bedroom. It seems reasonable to me that a partner should be willing to sleep with their girlfriend even in a bed they think isn't quite as nice if they're living with them and in a relationship.
In all other ways we still seem to be getting on well as a couple - spending time together, having sex, not having any major arguments... it's just this issue.
How can I encourage him to sleep in my bed again?