As a general rule, you must continue using hair loss treatments in order to maintain the results you've seen on them.

However do not fret. This is purely a mindset issue. You brush your teeth daily for the rest of your life - in fact two or three times a day, plus flossing, to avoid tooth decay. You shampoo every day. You shower every day. You shave every day - all to reduce the degradation of your health and appearance. This is no different. Hair Loss Treatments are like brushing your teeth. Instead of avoiding tooth decay you're avoiding hair decay.

If you're on multiple treatments and seeing success, some of this hair regrowth is likely a direct consequence of one of them. Rogaine Foam for example. Any such "rogaine-dependent hair" will gradually fall out if you stop Rogaine treatment.

If you're on Propecia, which is usually for maintenance, you may be able to reduce the Rogaine applications and still maintain the hair, but don't count on Propecia alone to protect and retain all the new hair grown from the combination protocol.