An hour sounds good to me. And if you don't feel like you did much in that hour, then maybe it's not the time but how hard you rode during that time. Get a computer if you don't already have one, and set mileage and/or cadence goals for yourself. Start off at whatever pace you feel comfortable with and go from there. Keep bumping the mileage goal up every time/every few times you ride while keeping the time the same.

two cents from the new kid