long term storage

The biggest problem with non heated storage is the dampness from frost in the ground coming through the cement. Rodents are second.
My favourite is a wooden barn, in the loft where there is air flow through the wood siding and the floor stays dry. As long as the storage has mice and rat control.
I bought a 55 vw that had been stripped to bare metal and stored for 11 years in a barn and didn't have any rust on it.
Heated storage is best though.