Years ago I used the old Firefox addon Shelve to automatically archive the vast majority of web pages I visited.

http://shelve.sourceforge.net/

The main disadvantage was disk space. This is particularly true when some pages are 10 MB or larger. I would periodically prune the archive directory for this reason.

I stopped using Shelve when I started running out of disk space, and now I can't use Shelve because the addon is no longer supported. The author of Shelve has some suggestions for software with similar functionality:

https://groups.google.com/forum/#!topic/shelve-firefox-addon...