Have you thought about getting a travel package instead? IMO, a much better (value-wise) use of points. In this circumstance, you could value each of those 20K points as one mile/point and figure your cost-benefit accordingly. If I were looking at it this way and needed one more night for the 20K, I'd take it.

BTW, the hotel portion of the travel package is good for one year and generally can be extended for one year without charge.

Pat