I have never used SpiderOak, but have seen it discussed here so I think there might be interest in this.
Humble is running a "Software Bundle 2" that has a 1 year license for SpiderOak One cloud backup with 1TB of storage in the $15 tier. The 1TB plan usually costs $12 per month. So if you were looking at SpiderOak for backup, this might be a cheap way to get started.
I don't know if this can be used to add a year to an existing plan.
The blurb says this about existing accounts: "License will overwrite any existing licenses during redemption and remaining credit will not be refunded". So for people with existing accounts, I don't know if you can hang onto this license and activate it just before your existing one expires or if you have to activate it within some short period. But if you're on a month-to-month plan, this seems like a no brainer.
Note that if you purchase the $15 tier, you get a bunch of other software too, but none of it looked particularly interesting to me. Except maybe the Winx Media Trans which is part of the $1 tier.
The bundle is live for another 9 days from now: