Originally Posted by jsloan

If the currently-published schedule is agreeable, there is absolutely no advantage to waiting. If there's a schedule change, you now have the ability to pick any UA flight that you wish, and keep P/PZ regardless of the current availability, or to get a refund if necessary. If there's no schedule change, then you don't have anything to worry about.

In the vast majority of cases, a schedule change is a good thing for the traveler.