Quote Originally Posted by Rafal Lukawiecki View Post
as no amount of replenisher will remove the silver that is already in the fixer, unless you remove the solution itself—now, if this is incorrect, please let me know, as I am eager to know.
Well, although this is correct, it's not the whole story. When you replenish, you don't REMOVE silver, but the fresh replenisher being added will dilute byproducts; thus you control silver concentration by changing the replenishment rate (solution being removed changes volume, but not concentration).

I don't know that there would be any advantage to replenishment other than the tanks staying in a steady-state condition. You're already doing good by using a 2-bath fixer and John's Silver Magnet. (Anybody doing any volume without something like the Magnet, or better, is missing out in my opinion.)