Joseb: Your question got me thinking wrt long term data storage as a backup to a NAS. While I do not offer any answers or suggestions, I think it may offer some interesting discussions and thoughts from the learned members here.
Personally I try not to use cloud storage, although with iPhones, iPad, etc., I do use iCloud for up to 5GB storage. Rightly or wrongly, I feel that the many offerings of Cloud storage, especially those that are free, come with the knowledge that many will scan your data for their own benefit. ('There is no such thing as a free meal'...) Also my use is for personal, home, use; I appreciate that many, if not the majority of NAS users back up their professional work data.
Looking at longer term storage, e.g. 1, 2, 5, 10 years, what are the options for NAS users? DVD, BDR, SSD, HDD, Cloud, others? (I think paper tape, if anybody remembers that, can be omitted); Any thoughts as to preferred or recommended methods for different types of user? Also, perhaps, where to store? Garage or workshop; partition on a friends NAS; Secure lockup... Storage environmental effects may/will be important, too.