So long as you have a backup of your backup ...
Not sure exactly of what all goes on, though I believe the way FF's sessions work is something like...
FF closed, a sessionstore.js file should exist in your
Profile folder
Additionally, various "backups" exist in /sessionstore-backups/
When you open FF...
sessionstore.js is used to restore your session (either manually or automatically, depending on your settings)
& at the same time it "vanishes", having moved to /sessionstore-backups/previous.js
When you quit FF, FF's session at that point, is written back out to sessionstore.js
Something of that nature.
IMO, with FF closed, if you simply copy the sessionstore.js file, & the /sessionstore-backups/ directory, from the old to the new, then open the new, you should be OK (again with the session opening either automatically or manually, depending on your settings). (Now you can't
not open that session, quit FF & restart, because at that point, your [prior] session data is gone, having been replaced with that of your last quit... except that it
may exist as one of the other backups in /sessionstore-backups/.)
Fire 750, bring back 250.
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.19) Gecko/20110420 SeaMonkey/2.0.14 Pinball CopyURL+ FetchTextURL FlashGot NoScript