How do you manage inks that have passed their recommended shelf-life?

Hello, we print food packaging gable top and we are using solvants inks type. We still using inks that the expiry dates are already overlopped. During the external audit, the auditor marked this point as non conformity. But still not find a solution to solve as we canno't threw this quantity just for the expiry date. Any recommendations, Thanks.

Have you tried discussing with your ink supplier?
They may be able to advise what factor(s) limits the shelf life, such that you could perform some sort of analysis to formally verify each time you need to consider an extension.

They may also be able to offer an extension themselves, possibly by analysing either one of their own retained samples or from a sample drawn from your stock.