The latest end date is either 31 days out or 7 depending on circumstances. It will be 31 days out if the grant of the waitlist would result in points going into a holding account. For example, suppose you have a reservation that costs 120 points and are waitlisting to switch to another at the same time that costs 115 points. If that switch was made less than 31 days out, you would lose 5 points to the holding account by the cancellation of the original reservation and setting up the waitlisted reservation. Thus, that waitlist is good only to 31 days out to avoid having anything go into a holding account. As long as there is not any holding account issue, you can waitlist up to 7 days out and you can do that when you call to waitlist, i.e., you don't have to call again before 31 days out to extend as long as you set it up for 7 days out to begin with.