Data hoarding is a deep rabbit hole that can consume a lot of time, money and effort. Used to hoard rare stuff but had to stop for my own good.

If you're grabbing lots of things because they meet some definition of rare, yeah.

If you're grabbing 720p of things you actually watched, then at 4 hours at day and 1.5Mbps an entire year of recordings would be less than a terabyte. So I'd estimate this as a $1-5 per month hobby and the time/effort shouldn't be too bad either. If they reach small NAS territory then that's a useful thing to learn. They just need to limit the 4K content.

However, it's satisfying to be able to smugly watch/listen to content that becomes unavailable due to it being old or unpopular or even complicated by rights issues.

Just yesterday, I was watching Digging The Greats on YouTube, discussing De La Soul's Three Feet High and Rising. He can't even recreate the beat/mix on YouTube as it would get flagged for copyright. It was unavailable for streaming/download until 2023 due to licensing issues.

My go-to example of disappearing media is the third season of Monkey Dust that ran into problems with music licensing and so it was never available on DVD and will never be screened again. (Available through nautical methods)

Yeah, just like collecting stamps or other similar hobbies. So what?