I had been off the bike for a few years. When I started back up I limited my rides to a 10 mile loop with 650 ft. of elevation gain. Initially that 10 mile loop would leave me completely spent. I've slowly worked up to where I'm easily doing 20 mile rides with twice the elevation gain and have done some 30 mile rides. Forget about expectations at first. Just ride and listen to what your body tells you. You might be surprised at how much muscle memory you retain even after over a year of not riding. Just don't push yourself too much too soon.