Other Options for Storing Pages Rated 3 out of 5 stars
I have found unMHT to be most reliable at storing single pages for viewing later, and it can save all open tabs in one command reliably (to one combined file, or separate files).
I haven't used the others in a while but will try to remember as best I can.
DownThemAll worked good for getting a download of all the components of a page. Particularly useful if you had a site with numerous direct links to media like songs or text files.
ScrapBook (this), if I remember right, allowed you to download not only the page you were on, but also completely get all pages reached through links within the first page? But it seemed more unreliable than MHT and I eventually gave up on it.
Pocket allowed you to take just the links and then reopen them elsewhere.
Just thought I'd offer up options to people. Not sure many of them are working on newer FF, but unMHT is going fine, at least :-)