Once you can feel good-sized follicles (gobstoppers, as Adam calls them ), he has done his job, and the follicular development will continue without contact with a male. If you are only breeding him to one female though, you can keep putting him in until you see ovulation, or you don't see any more copulations. Depending on when she starts developing follicles, this could be in December, or in April. Once you get the feel for palpating, you can really measure the progress of the follicles once they reach a certain point (you can't really feel them until they are relatively large).

-Evan