I was staring at a 4x5 slide I developed last night, and I started wondering whether it or a C-41 negative would last longer. I did a quick search and found this YouTube video where the speaker references an issue of Photoklassica that stated (paraphrased) that E6 slides have an archival life of 200 years which is 3 to 4 times the lifespan of C-41. He mentions it at 3:20.

You could argue that I'll be dead long before my C-41 negatives noticeably decay. However, I do intend to leave a few treasures behind for posterity. I'm sure many of you do too. This information makes me more inclined to shoot more LF slides because they're comfortable to view. Medium format and 35mm slides are so much less enjoyable at a glance on a light table that I wouldn't mind sparing my sanity and sticking to C-41 for them.

Do any of you have good links to share (or personal experience) that confirm this claim by Photoklassica? I'm doing more research on archiving my work in general.