This is yet to be discovered, there are many men, like myself, who have been involved for years and we are still making gains. As you grow and become bigger it does become increasingly difficult to gain but this is dealt with by increasing the intensity of the workouts or including more powerful methods.
SRT is a great routine that is at the top of the charts as far as gaining with consistency. I have gained far more than I could have ever dreamed of and to keep that going I always am inventing new exercise, routines or using equipment to speed the process. Best equipment, that every PE practitioner should have are The
BathMate, the
SizeGenetics and the
LengthMaster, with these tools and the
SRT Workout there seems to be little limitation to growing.