ugh. Maybe it's a chick-thing, but I groan at the thought of checking out every morning. And as my business trips put me in one place for (at least) several days, I opted for Marriott Rewards. Even get credit for my room-service breakfast! Assuming you wait until the max level of points to redeem, $150 per stay is the break even-point. er, actually twice that with the 5-stay bonus.
But kudos to MileKing, to accomplish his feat you'd have to spend $30,000!