You could save the web pages themselves as .html if you wanted. I'm not sure how many pages it spans, but it's an option. (As mentioned by Enguin)
Copying everything into a doc/word/notepad is probably the better option, but as you mentioned it would be tedious.
Keep in mind, even if the site goes down, previous versions are available using archival services such as the way back machine. Assuming you aren't typing this on-site, you can save it elsewhere before posting, and the archives give you plenty of leisure on saving the backlog.
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