Unfortunately my friends would probably see winning too often as a good reason to collude against me. Although collusion would lower the average length of a game, it would probably raise the chance any individual friend wanted to play with me (because they would be winning more often, on average). Although I agree with you that that's a strategy I hadn't considered, which is quite an oversight given the content of the post!

Khoth has correctly identified that surely the best strategy is to convince my friends to play a similar but superior game, although this isn't always possible. For example with the horse-traders I try to play Catan and with the roll-and-movers I play Pirates. Unfortunately if there are too many of both groups then the only thing they can compromise on is Monopoly, and I don't have the persuasive skills to overcome the inertia.

However the fact there are a whole bunch of superior games to Monopoly sort of breaks the analogy I was driving at so I left it out of the main body of the post.