I have a room in the house that my lovely wife lets me do whatever in. Plus three in what was supposed to be the formal dining room to entertain guests. At this point it isn't really a question of whether I can fit another pinball machine, its whether I want to throw out enough of my other stuff to fit another.
It took a while to get to this point though. Lots of tense negotiations and setting/breaking boundaries. I think she settled on the point we are at now when I started building up a route. Then whatever was at home seemed minor compared to the hundred some odd coin-op devices I have in other places. She at least gets to play the ones here.
She does play some, but I've learned the hard way never to buy any pinball machines for her. Her favorite game outside of the house was Stargate. Her interest in it died the day it came home. She was pretty pissed I bought it too, because she didn't like the idea of me buying games she liked to get her to play more. Now my strategy is just to have her rate the games we have when I start thinking about letting one go. I've only sold one game she really liked.