JMR007 unfortunately they wont be able to extend those to cat 5 or higher since those are all promo certs. There are PLENTY of cat 4's everywhere basically. Now if you're trying to go on a traditionally busy time (weekend/weekday either or) of course it's not gonna be available at as many. Consider the fact that there are millions of other rewards members that like to use their promo certs and points when they can. My advise is plan ahead and if there's availability..........BOOK IT!!!!!!!! you can always cancel using a cert/pts, if you wanna change it you can if not just cancel within the cxl policy. That's one thing that keeps me going to Marriott, for most of their hotels u can cxl same day whether it's 4pm or 6pm. When you call in or check online, take in consideration that they are quoting you availability at the time you're inquiring and only way to guarantee the reservation is to BOOK IT. Only thing else i can say if you didn't know about them, check your account regularly, Marriott shouldn't have to hold your hand through everything and tell you everyday what's going on with your account.