the first two weeks of December are lowest of the low for demand.
see attached.
UA says they are increasing Hawaii service as of December 20 - that's when the peak starts.
while, as indicated, 5 x/ day is the standard service on lax/hnl, there are times during the year, during low season lulls, when that is decreased, especially on non-peak times. they have the data that tells them when capacity is needed and when it's not, and they adjust accordingly.
http://newsroom.united.com/2017-06-1...-Daily-Flights