The bleach typically lasts forever. Every dozen rolls it may be advisable to add 10 g/l Ammonium Bromide and get pH back down below 7. Not sure how to replenish this specific C-41 fixer.
Konica posted a patent US6225018, in which formulas and procedures for replenished C-41 development are shown. The formulas in this patent use a different bleach and a much stronger fixer. You may not be able to find the ingredients for their bleach, but the fixer should be doable. This would give you a replenishable fixer process that's likely going to work.