I may have damaged some tapes

I didn't really think this belonged in Off-topic, but it didn't really seem to fit anywhere else. I've bought quite a few tapes off of eBay of Kids' WB recordings, in hopes of preserving as much Pokémon media as possible. They contained some promos and stuff I've never seen anywhere else. Some of these I've already ripped and shared here, but most is still not digitized.

Anyway, last winter, I realized at some point that some of them were right on top of my bedroom's floor vent. Most were in a cardboard box, but some were loose. Hot air was blowing directly on to the tape itself for some of them. It really freaked me out and I moved them, but I was afraid it was too late. To this day, I haven't checked them, mostly out of fear that they're badly damaged. For all I know, I may have had the last remaining copy of some of the content on them. What are my chances of recovering the video?