If this were a closed loop cycle for the IPA, I could see an issue. Between normal losses using the IPA in my projects, disposing of fairly diluted concentrates while also replenishing the IPA with fresh stock doesn’t seem like it would allow for for dangerous levels of peroxide buildup.

Testing the IPA is a good route to take though. If peroxides are coming across during distillation or if the dirty IPA contains measurable peroxides, that would be good data to have.

I am not above spending the cash to have an analysis done on the purity of my IPA either. It would be a hair expensive, but data is invaluable.