You can NOT maintain a 10lb lean muscle growth rate year after year naturally. You WILL come to a point where unless AS is introduced you will grow no more. Its called reaching your maximum genetic potential. AS can assist in breaking through this barrier, but naturally gains do cease. It sucks, but if your going to lift naturally you have to be realistic. Can you gain 10lbs a year for 1,2 matbe 3 years, sure you can, however it will come to a halt. It is this reason that you dont see heavywieght BB pros who are all natural, why, because they do not exist.