yea I found the exact folder by looking at the "created" time stamp and comparing to the backup log in the browser extension. 

The important thing is that it's in the profile folder, so when I use MozBackup to backup my Firefox settings, the Eversync backups will be included. 

I use ES only for the frequent auto backups, nothing else.  Firefox only backs up bookmarks once a day.  I don't use the ES sync.  The built-in Firefox sync is better imo, it's faster and and uses less resources, so I turn it off in ES. 

Thank you!  I wasn't expecting anyone to respond.  It's good to know for backup purposes. 

So I found the exact folder:

C:\Users\{USER_NAME}\AppData\Roaming\Mozilla\Firefox\Profiles\{PROFILE_NAME}\storage\default\moz-extension+++653ad1e0-2b4c-4240-975e-95b7ea437fdc\idb\431751663645-3ca4db12e-0.files

I wanted to ask the same thing.  Are the local backups stored somewhere in the FF profile folder?