For assault support, i.e. CH-46E and CH-53E you can plan on something approximating the following:
6 months of Marine Expeditionary Unit (MEU) workups, where you're gone on various exercises, on and off the ship for maybe 1-2 weeks per month average. That's heavily stacked toward the end of the 6 months.
That period is followed by a (approximately) 6 month deployment aboard a LHD or LHA amphibious ship. Come home, and you have about 17 months before starting that cycle again.
In the meantime, you'll probably do 2 Combined Arms Exercises (CAX), which are about 3 wks ea. Then there are 1 or 2 other random deployments you'll end up doing. That is, unless some contingency comes up and they need you on a ship again on a moment's notice.
Phrogs phorever