Apparently if you stay fewer times, they value you more and make the offers more lucrative. For instance 1 free night / 2 stays. If you stay a lot, then they devalue you by making you stay 20-25 times to get anything ... I have dramatically reduced my nights at Marriott from about 100 down to about 20 to see what "MegaBonus" plan I get next year. I suspect that they believe if you stay a large number of times, that you will continue to do so no matter how poorly they treat you.