Depends on many things. But if you stay dedicated I think you will be able to gain the length in 6-18 months, the girth is a lot more tricky and could take between 1-3 years maybe.
I Sure Hope So
Its been 3 months for me. I’ve gained .5”el so yes I hope 1” is achievable. I would rather have 1” girth than length though! I hope it’s possible in a year! I have been doing Jelqing,bathmate,clamping for the most part all girth wise exercises.
"You may only go as far as the tractor will take you. Then you must walk" -myself