Roughly speaking, the hormone therapy halves the recurrence rate. If it did recur, you might find yourself on hormone therapy for life.
Having said that, You've done probably the most important part of the hormone therapy, but I think all oncologists would say just 1 year is on the short side for a Gleason 9. Stopping now will probably increase your chance of recurrence, but not as much as never having used hormone therapy at all, so less than double the chance. Your oncologist might be able to give you an idea of the extra risk of stopping early.