It doesn't feel like google has been a good steward of these archives. They blended usenet archives and google groups together in a really annoying way, content has erratically gone missing (see the lwn link that hprotagonist posted), and have seemingly lost interest overall--the whole google groups product has seemed neglected for years. My guess is the only reason it hasn't been sun-setted is that someone high up needs to remember it to kill it.

It really seems to me that archive.org, or some similar organisation, should petition Google to donate their Usenet archive, which they clearly don't care about, to them. Or possibly buy it off them.

It's a long shot since it would require Google to actually do something with a dataset they clearly don't care about, but they could get some good corporate PR points almost for free.

There have been reports that some of those posts have been vanishing from Google Groups[0].

It's nice that this person/org is hosting these, but I'd feel more comfortable if archive.org (and perhaps another org or two) mirrored them as well. History shouldn't be dependent on some random person/org paying to host them. I thought things would be safe with Google and I was wrong. I'm definitely less confident that usenetarchives.com will be around forever.

[0] https://lwn.net/Articles/827233/