Followup on original post ... Saw the night I wanted available for reasonable price but system would not let me reserve it. Same for 2 calls to Bonvoy. Finally called hotel and tried the in-houe reservations. They were really helpful and got me the room for the added night. Said plenty of rooms so not sure what was going on.If you book using your Bonvoy account you should be able to modify the room for the new rate without canceling, it's super easy! I am starting to book at Marriott hotels more frequently and their rates bounce up and down so much. The ridiculous rates (like 1k+) seem like super low inventory due to conferences/events. I imagine those can take hundreds of rooms out of commission and thus they raise the rates on their remaining inventory for the people who don't know any better (or don't care) and fork over a fortune. Looking at the "flexible date" calendar is always interesting to see how the rates vary for each night. Definitely keep checking rates. I have found the best rates to happen a few months prior to the trip (and sometimes in the weeks prior), rates really far out tend to be really high (such as for 2024). But since they change so often, the frequent checker and not the early bird probably gets the worm!