Note that Firefox 37.0.2 has been released recently, so you are behind on updates with Firefox 36.

Do all other browser.sessionstore prefs have the default value?

Does Firefox create a sessionstore.js file when you close Firefox (I assume not if an older session is restored)?

Are there any sessionstore files in the main profile folder (i.e. not the js files in sessionstore-backups are meant)?

You can try to rename the sessionstore-backups folder to see if a new folder gets created.

Thank you for the thoughts.

Since restarting Firefox earlier this evening (killed its process and its two plugin companions), both recovery.js and recovery.bak have been updated at two-minute intervals (or rather, recovery.js is renamed to .bak and then the .js file is replaced), but aside from the update to the .interval parm to 120000 I made no changes at all. Puzzling.

(After that kill+restart, nothing was updated in the sessionstore-backups folder.)

In the profile folder itself there are older, earlier-version .js files, but I renamed them all long since to values such as "recovery-mm-dd-yy-hh.js" and I don't believe they are affecting anything.

I have attached an image of my sessionstore settings. Along with the update to browser.sessionstore.interval, the only other changes from the default are to max_tabs_undo -- I set that way up a couple of months ago -- and to max_window_undo, set to 5.

Later tonight I will go through the kill+restart once more, but with the updates I'm seeing now to the timestamps in sessionstore-backups I expect better results afterward.

Follow-up: Firefox continued to update recovery.js and recovery.bak in the sessionstore-backups profile folder until about 2:30am this morning; and then it stopped doing so until I killed its process and restarted it around 12:30pm.

The recovery files have been updated on the selected 2-minute cycle since then. We'll see when/if that stops working again.

It's been a week since we've heard back from you. Is this still an issue?

Thank you for the follow-up. What continues to occur is around 12 and 20 hours of normal updates to the sessionstore files, then -- with no other apparent symptom -- nothing further until either I force and restart FF or it crashes and I allow it to restart.

So far I have found nothing unusual or consistent in the timing here. I continue to try to isolate something here which might be associated with the errors that persist.

Happily the comment below can be partially retracted. Having not had a FF failure for two days, in spite of the "fixed" sessionstore files, one of the windows after session restoration was so far out of sync with its current tab list that I accused Firefox of worse behavior than is actually in evidence. Sorry.

| (In the meantime FF has crashed once more, and upon restore brought back a window | containing six tabs that I haven't had active for two weeks: that is, neither it nor its tabs | have been part of any of the session files for that period of time. Yet, here it is again. | | The cat came back ..)

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Will give that a try, thank you for the suggestion and pointers.

There appears to be little or no information in those references concerning whether copying the sessionstore files is a legitimate step when migrating information from an old profile, or how a new profile can be validated in this case without them; short of recreating each window, I suppose.

Late follow-up: creating a new profile and upgrading to version 38.0.1 seem to have alleviated the sessionstore problems. (I don't know whether the new profile by itself would have been sufficient here, as for the experiments I did I may have copied too much information across from the original profile -- and the sessionstore files weren't consistently updated.)

We had a long thread about 16 months ago where Firefox stopped updating the session file sooner, but we never solved it: Crashing, and restored session missing some tabs that were open. I'm glad to hear you found a workaround!

Thanks once more for the suggestions and follow-ups ..