It looks like the 1 year option was introduced maybe 2 years ago:

https://www.reddit.com/r/backblaze/comments/175haik/is_upgra...

(Ironic that their ex-employee wrote: "In this case, it is always kind of scary for Backblaze to just quietly change a setting from one setting to a different setting in the product for the customer without the customer taking that action themselves." — when that's what happened in this case.)

I don't use Backblaze, but I found the Version History doc for you:

https://www.backblaze.com/computer-backup/docs/version-histo...

Seems like whatever version is not currently on your local disk would be chargeable.