I can answer about the bookmarks, which are stored with your history in the places.sqlite database. I'm not familiar with changes to saved logins.

Firefox has changed in three respects with respect to bookmark backups (not sure of the exact versions):

(1) If there were no changes in your bookmarks since the last backup, a new file is not created (this allows you to keep more different backups for a longer period of time);

(2) The files are now compressed and have a different file extension - previously .json and now .jsonlz4; and

(3) Backups are made when Firefox has been idle for a while instead of at shutdown, since the process sometimes failed or caused Firefox to hang at shutdown.

Another user complained about #3 since he would promptly close Firefox when he was done with it, not leaving enough idle time. This thread has the story: No more automatic backup of bookmarks since FF 29/30 ?

Not sure whether any of those are relevant to your scenario.

Hello baruch, yes you are correct, from Firefox 32 and above the signons.sqlite is no longer used and the file logins.json is used instead. If you want to force Firefox to re-import the passwords from the signons.sqlite file then see the last paragraph in the next link : Password Manager Troubleshooting

thank you

@jscher2000 Thanks for the info you posted it did help clear up the mystery. I too generally close the browser when finished using it --especially since a lot of the work I do on the PC is off-line anyway. This afternoon I did get involved in something and did leave the browser open and unused for an extended period of time. I just looked in the profile 'bookmarkbackups' directory and infact did see a current/recent backup. Strangely however over the past several days I have made bookmark additions and deletions and that activity did not trigger an automatic backup --unless that was because the browser was never left 'idle'.

Can the idle time period be adjusted? If so how?

@ideato Thanks for the info you posted it did help clear up where passwords were saved.

Curiously since I posted the question I have seen some 'old' passwords show today's date in the Last Used column so I will watch it for a while to verify if infact it is working properly.

Can I copy my passwords from one PC to another by simply copying the logins.json file (along with key3.db) as I have been doing for years with the signons.sqlite file

(Bookmark backups)

If I'm reading the code correctly, the idle time is 8 minutes. If three days pass without a backup, the idle time is cut in half to 4 minutes. As far as I can tell, these values are hardcoded and there are no preferences to adjust them.

@jscher2000 For years (ever since Netscape) I've copied bookmarks from one PC to another by simply copying the 'bookmarks' file --more recently with the .json extension.

Can I continue to copy the bookmarks-2014-11-06_5172_iICCDvD5jwWSfujdFlu1uw==.jsonlz4 file between PCs, or will the 'hash' and/or compression cause it to be unique to the PC it was created on?

The compressed jsonlz4 format is only used for automatically created bookmark backups. You can still create an uncompressed .json backup manually in the Bookmarks Manager (Library). It shouldn't be a problem to restore a compressed jsonlz4 backup on other computers assuming that you have a recent Firefox version that supports this format.

Do you close Firefox every day or at least sometimes? If you keep open Firefox all the time then it can take some time for a new backup to get created.