Already the link rot on youtube is significant. Very often I will find links like "listen to this music it's good", you go to youtube and not even the metadata is left, it's just an error page so you have no idea what it even was.
I have yet to see a definitive answer re true originals being kept vs iterations of transcodes as the preferred codec changes.
Or similar questions about deleted videos getting flagged vs scrubbed, etc.
Or who might ever have access to originals in either case.
It actually seems better from when I last looked at it, but you can you still hear skipping and audio jitter around spots like at 0:18. I've seen similar behavior on Twitter video uploads over the last few years.
I'll intentionally duplicate playlist entries (two different uploaders) as a buffer against rot.