I'd say it's quite heavily archived:
http://web.archive.org/web/*/vogons.org

Unfortunately that’s not so once you dig deeper.

What I've found in using Wayback Machine over the last few weeks in hopes of scraping useful content from archives of dead forums, is that the crawlers may only archive to a depth of 2 or 3. I just used your link and navigated to three random threads (in different subforums for different capture dates) and in all three cases I could get to the forum index but the individual threads aren't archived. I've run into this issue consistently with other forums. Depending on the forum architecture, sometimes you can get to the first page of a thread but no further. In other cases you can't even make it to the index. In virtually all cases, search functions are broken so even if the content was archived, finding what you're looking for is next to impossible.

We have friends within ArchiveTeam and can run a full forum backup for archive.org (aside from private messages) at any time (as long as Qbix/Snover think the server can handle the strain). Forums require special attention that the standard Wayback crawler cannot handle by default.

Aside from that, I'm not sure what Qbix/Snover have set up for backups at the back end, I'd have to ask them.