Sorry....meant to say that the Halloween parties are selling out. I'm sure some of the Christmas Parties will, too. But not weeks in advance. Most of the time it's just a day or two out that specific dates will sell-out. (Tonight's
MNSSHP is sold out.)
In theory they would have the same number of tickets available for each night. The logic is pretty simple. On days with the highest (historical) demand, they stick with full price and hope to sell out. Days which typically have smaller crowds will offer a discount. If they happen to sell-out a discounted night...so be it.
Generally speaking, the mid-week dates are most likely to be discounted while the weekends are full price.