On Odysee I've followed a couple of channels but I rarely check what they upload
https://odysee.com/@VtuberArchives:1
https://odysee.com/@Vtuber_Archives:8
Currently Odysee seems like a good place to archive this content. Currently they use the LBRY backend so you can interact directly with the LBRY blockchain daemon, and see all the content they have posted, as well as the duration, and file size.
Once Odysee moves fully to the Arweave (AR) protocol, I don't know if there will be an easy way to look up this information. Odysee also mentioned that they may not store videos forever, but that they may expire after a certain time, like after a year or so. This makes sense for content creators who release content periodically, however, it would not be good for archival purposes.
The idea with Arweave is that you can pay for a video to be hosted indefinitely in a decentralized fashion, with different relays. That is, pay right now $50 dollars (or whatever the cost may be), and that guarantees that the video is "hosted for the next 200 years", or at least that's how they advertise it.
Why is this? Well, the idea is that storage costs are coming down all the time, so it will be possible to store information cheaper in the future than it is now, particularly if there are many nodes replicating the information.