tuc, I think it totally depends on the person and the type of training you're willing to do. Look at the way Nathan Holle(second #4 closer) trains. If you focus this much time into grip training, chances are that your strongman shit will have to slow down. Training for the #4 is way too specific and limited training-wise for me personally. You could definately do it, just the time depends on how you train, injuries, hand therapy, etc.
Backlash, 3 people have closed it now bro. A couple more are 'damn' close.
By the way, I was witnessed last night for my #3 certification. I slammed it and actually ground it back and forth, then hit another solid rep that clicked. Hehe.