These pavilion you mentioned do the hot ones. You are right that if you would like to visit all of them, at least 5 days are needed. The possible methold to shorten the long queue is that you should leave for the expo park earliest in the morning, and make sure that you enter into the park in the first 20 visitors.

Ps: some pavilions open green channel for travelers with kids under 2 years old or elders over 65~70.