This debate comes up every year. There are 3 months left to the year. If you need 10 stays that is only 3 stays a month which is less than one a week. If Diamond is that important to you then spend the $ to stay (and before anybody starts flaming me, I pay for all of my stays out of my own pocket). You have Platinum already with your 15 stays. Perhaps your travel patterns have changed for the next few years and that's all you really need?