Here's what we did
For our purchase, the annual week we were buying was going to happen right around the time the county registered our deed and notified the resort.
So after I had signed the sales agreement, paid for the ts, (money is still in escrow), and then ok'd a copy of the deed, I then asked the seller to put the week in my name. I then followed up with the resort, and confirmed that we are registered for the unit that week.
So my suggestion is to ask the seller to bank the week, if that's what you want to do, assuming there are no more hurdles left to the sale except the registry of deeds.
FWIW.