
UY has nothing to do with booking a villa. You can book a villa any time you want as long as you have the points at time of travel.
DH and I travel Oct-Dec...we have a Dec UY (Dec1 of current year to Nov 31 of following year) which is very risky for that travel time. October would be better for us. Because we travel at the end of our UY if we had to cancel a trip less than 30-31 days from check in, those points go into holding. If our canceled trip is say Oct 10-20, then we only have until the end of that Dec UY or Nov 31 to use those points. It is hard to book a trip that time of year on short notice. If our UY were Oct then we would have to the following Sept 31 to book a new trip--because we would be at the beginning of our UY. I hope that makes sense.
Someone will come along shortly and correct me if I am wrong--but that is the importance of UY. I had no clue about UY when we purchased--or I would have asked for October. We have never had to cancel a trip thank goodness and we are not confined to a specific time of travel--so we are OK with Dec thus far.