I am not aware of any archival stability issues with ECN-II when processed in the intended chmistry. Older color films (whether ECN, early ECN-II, C-22, early C-41, E4, and early E6 ones) clearly had archival issues. But I was under the impression that these have mostly been solved in today's films and chemistry. I doubt you would find your images gone in 30 years. We have some old ECN-II negatives that were taken of me as a baby, and there are still images on them. Again, I doubt this is an issue worth considering.
Originally Posted by holmburgers