Thanks Mark. I think I'm going to buy another set of Jobo flasks, with proper air-tight lids (my Jobo flasks don't have lids at the moment, that's how I received them from the seller of the machine) and apply the exhaustion accounting for bleach and fix.

I searched through the site again regarding reuse times (using "C41 reuse" as keywords, lots of info). People says things like increasing time after X rolls, but don't specify the way they use their chemistry (how much they prepare, use, pour back in the flask, how much real reuse is that).

The time increase appears to be small, something like:
3:15; 3:30; (3:45 for a third process).
or even:
3:15; 3:23; (3:31 for a third process).