Are you looking for free, unlimited, off-site cloud storage for your backups? Why not try Usenet? You can encrypt your backup files, upload them and download them later if you need them. There are Usenet providers who offer up to 3 years retention, so you should be ok.
A colleague mentioned this idea last week, to encrypt your backups and upload them to Usenet. I took his idea and made a shell script to do exactly just that. The script takes a single file and a newspost name as argument and encrypts, rars, pars and uploads the file to Usenet, where you can download it up to three years later.