There's usually a board every month for PLC. It depends on the district that you're in. I would advise you to not wait until March or April. I would just go down to the office and sign up. The closer you get to summer, the less the OSO will want to be bothered with you because usually he/she has almost closed out for the year by that time. Going to OCS is not like going to enlisted boot camp. OCS only has so many beds per summer for kids. If you wait until the last minute you might find yourself out in the cold. Also, the way things are going down, the Marine Corps is lowering its requirement for pilots, so you really might not get a slot if you wait until the last minute. I hope this helps.