I have a my Firefox profile and a copy of its folder. After a certain amount of time launching Firefox with this profile, the history and cookies are missing in the browser, as well as some other preferences and data. What I do is that I close Firefox, delete the profile folder, duplicate the copy to a new copy and rename the original copy to match the profile folder name. The next time I launch Firefox history and cookies are here again. Then after 3 or 4 launches, they've disappeared again, so here I go again with the copies. I don't know what causes the profile folder not to work after a few launches. One time the history was there again even after rebooting the computer, most of the time it disappears after a few hours (after a few relaunches of Firefox). The profile originally became corrupted when I performed a cold shutdown of my computer while Firefox was open. I remember that when I booted again, my profile was well; it was at the next Firefox launch that the data was missing. I opened the sqlite files with the sqlite3 command line and they looked clean. Next time I launched Firefox the data was available again. I made a copy of the folder in case of, and there I am with the merry-go-round of copies.