If you keep a steady routine and are in good health the first year it’s possible to gain around an inch on average. As far as girth I would say on average you could expect between .5 and .75 inches the first year. I have been at PE for about 10 months, and I have gained about .85 inches. Keep in mind I simply manual stretch and jelq every other day for only about 20 minutes. If you put in a half hour or more, more days a week, and mix some clamping and hanging your in good shape. Everyone is different, but what I said above is what I feel you can reasonably achieve.