Always the $100 question isn't it. I think we all get to that place at some stage whether due to $$$ or room or both. I don't think it is a bad idea to turn some machines over every now and again to keep the collection fresh and your interest in the machines going.
The recent news of Stern doing both X-MEN and Avengers pins has made this quandry bubble right to the surface, they should be both cracking games but I have to sell another cracking MARVEL pin to buy a new cracking MARVEL pin. I don't know if I should laugh or cry...... it's got me stuffed.