Originally Posted by
stephanos99
Who decides how many points it costs for a free night? Marriott or the individual hotel?
Marriott sets redemption rates.
Originally Posted by
stephanos99
which I felt was a safe buffer for any potential increase in points in the 18 days it would take me to collect all those points
There's really no such thing. This is always a risk, even when there's only a one day lag, let alone an 18 day lag.
Btw, if you'd waited, there's a very good chance that at some point the price would have gone back down. One of the features of dynamic pricing is frequent swings in redemption rates. Keep watching and if the price goes down you can rebook and get points refunded. Many of us have gotten multiple points refunds on a single reservation as the price progressively drops.