I guess the only party that actually does sell out always is HEA. However, I do not get why they don't put it up every day like the rest. For example, why don't they put it on a single night on Christmas week?
I mean, the most crowded week of the year, were it makes the most sense to spend more in a Dessert Party, so you're less crowded, and they don't open a single date? HEA, F!, JBJB, RoL, even Fantasy in the Sky - New Year Countdown has it on both shows on Dec 30th and 31st, yet Epcot has no dessert party on Dec 25th or any date after, probably until mid January. It is just weird that they lose an extra money opportunity like that.
They WOULD sell out if available on those dates, that's for sure.