13.3v resting seems to be a fully charged battery for storage. Even though BB says to fully charge their battery for storage there are white papers that have shown irreversible capacity loss when this is done, also temperature during this storage period of time contributes damage.
Link below for Calendar Aging and Lifetimes of LiFePO4 Batteries and Considerations for Repurposing. Downloadable pdf, it's not a short read.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://uwspace.uwaterloo.ca/bitstream/handle/10012/12177/Catton_John.pdf%3F&ved=2ahUKEwjpiJ2lgoboAhWKuZ4KHfD_D9oQFjAMegQIAhAB&usg=AOvVaw3H5362G8-RBulf3pJEDmWU&cshid=1583506056827