There are more people who can travel besides those listed below, but generally speaking, these are what typically use the space a system
category 1: emergency leave
category 2: active duty on orders
category 3: active duty on leave
category 4: families with deployed active duty sponsors
category 5: families of active duty sponsors living overseas travelling w/o the sponsor
category 6: retirees
I have hopped Cat V from Ramstein Germany to/from the states twice. Once in late September into McGuire and once in Early November into BWI. I've had good success travelling off-season. I am trying for the first time peak season this summer, mid-July, I booked one way commercial back here because we are returning the week before school starts. We know several Cat V travelers who missed the first 2 weeks of school waiting on a flight.
IMO, it's worth the money for the cadet to get home and relaxing rather than have them sit at a terminal for 2-3 days waiting for a flight (after all there are no college tuition expenses). And as mentioned previously, you would have to consider the costs of buying a late-purchase seat.