FWIW, an August UY is a good choice for those who normally vacation in the Sep - Dec timeframe. It could very well be that many of them purchased August specifically for that reason, and therefore are less inclined to sell it.
I have both a June UY and an August UY contract. If I ever decided to sell anything, it would be one of the June contracts, not the August one.
We purchased the June UY at OKW, in June 1993. I assumed at that time we got that use year simply because that's the same month we purchased.
We purchased the August UY resale, in 1997.