Spending night

Tonight at B's grandparents house we were all sitting by the fire and they said he could spend the night. He usually likes to hang out as long as possible and then go home and sleep in mommys bed. So tonight he said he might. Then later he said no. So his daddy says something to the effect of it being ok that he doesn't want to, that when B gets big he will stay the night and B says (matter of factly), "I am big, I just don't want to."