Usually 20 minutes ahead is sufficient. If it is a very busy park day then maybe 25-30 minutes. I would guess that the number of dining reservations allowed also correlates to the seating capacity for the dining package section. We usually prefer to sit mid way or further up in the mickey section, so no need to be the first to get a front row seat.
I'd show at least 30 minutes prior. When there last we saw the sections that were assigned for the Dessert Party and the Dining Package - those filled up at a moderate pace.
If you want a reasonable choice of seats, be in line at least 30 minutes before. The package line and FP line are the same and it can go down Sunseet BLVD a long way. Once inside, the line splits into FP area and package area.
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