No, you don't have to remain in the reserves at the end of your commitment. I would check on your contract numbers, I still believe that it is wings plus 8 years. Consider that by the time you leave the service, you would have more then likely invested 10 or more years. Why not stay 10 more until retirement. You can remain in the IRR (Individual ready reserve) and work on PME to earn your points (no pay) until retirement. Chances are you will never be called up in the IRR but you are there if your country needs you. Paid billets in the reserves can be tedious and there is the chance of being called up. The reserves will take up more of the slack as the military becomes more streamlined. In the future, reservists more so then ever will be an integral part of this nations military. I've accepted that and can tell that a paid billet in the reserves is incredibly rewarding and allows you to break up the routine of every day life. Each person is different.
Go to the Naval Reserves or Marine Reserves web pages to view the pay charts for drills for reservists. Good luck. Semper Fly, Frumby