I have used slightly diluted C-41 dev from a Tetanal kit before it was also quite a bit past its 12 roll use I added around 15 seconds for the diluted old developer and you will get useable images it just depends how you feel about whats on the film really if its something you put through a holga then go for it but if not might be worth sending to a lab

and yeah with the tetanal kit you do cut 30 seconds off in a rolling processor so may well be the same for you