Minor typo: This says 24 parties. I count 25 parties total, 11 sold out. I'm not sure which is intended.
Quick analysis:
Although this may be more sell-outs than ever before, it's still less than half the parties. Four out of the six September parties sold out, but none more than two days in advance. There are more September parties this year, so it should be safe to wait until a week before.
The October parties sold out earlier. Ignoring the Halloween night party, which sold out in August, and the 10/9 party which doesn't have a sell-out date given, only two had less than a week to go before selling out. Starting with the 10/27 party, the sell-outs were all at least a week earlier. So if you're looking at a late October date, consider buying no later than early October.
Of course both weather and prices will affect the sell-out dates, as we're already seeing with Halloween eve. And past experience is no guarantee of future results, so don't blame me if your ideal party sells out five minutes before you try to buy.