I believe at least the manually taken Snaphots will last forever. Just the automatic Daily ones last for three days (today-2 to today). At least they do for me.
However I think extending the retention of the automatic ones to a week or a month (can be optional) could be usefull.
The current backups seem to be stored in "%userprofile%\AppData\Roaming\Stardock\Fences\Backups" so you may want to copy them to your personal backup (can be schedulled via task scheduller).
Example batch File (please note ISODATE variable below is for US regional options (Month/Date/Year)
"c:\program files\winrar\rar.exe" a "C:\Backups\Fences\%ISODATE%.rar" "%userprofile%\AppData\Roaming\Stardock\Fences\Backups"