How Long Should You Wait Until Moving In Together? [Poll]

I was talking with someone the other night who believes that two people should not move in together until they get marriage. Otherwise one gets stuck in the comfort zone and there is no motivation to take it to the next level. The guy feels he doesn't have to buy the cow because he has the milk and while the woman may not be completely satisfied, she doesn't want to cause any riffs in the relationship. What do you think? Should you move in before getting married, and if so, how far into the relationship?