I think a 5L kit can in theory develop around 40 rolls. I am going to order the developers in bulk. I think the only way to get repeatability is to use one shot. To run a replenished E6 system, in my opinion, means control strips, densitometer, pH meters etc. Tony Santo has a video from 2014, he uses everything one shot. I may do the same. I can figure out my exact process time, I have a nice Jobo, which does an amazing job of temperature control. You need to measure the 1 L bottle temps usually the bath needs to be about 0.5°C higher, especially in a cool darkroom.
The Tetenal kits work, but the capacity claims are overrated. I have found 4-6 rolls per liter is repeatable, beyond that is a bit of a guessing game, at least with the Jobo. The first developer times need to be increased, it's a bit of a guessing game.
E6 is expensive, I don't drink, smoke, or drive fast cars. My wife told me tonight that she was shocked I didn't have fresh chemistry

. So I guess I'm going to go nuts. Now I know why pros ditched analog.
