It's not prohibitively expensive; all the large internet/cloud companies upgrade machines and drives on a ~3 year schedule and mostly keep the data online. Sto

It's not prohibitively expensive; all the large internet/cloud companies upgrade machines and drives on a ~3 year schedule and mostly keep the data online. Storage Moore's Law means that every upgrade let's you put the old data onto fewer new drives. Storage Moore's Law is slowing, but still makes this the most affordable option when taking durability into account. Offline storage is dangerous. Readers go obsolete. Media degrades. Data sets go missing. Protocols and storage formats become obsolete. Migrating data from one online storage to another while upgrading hardware solves a lot of these issues, the only exception being storage format for straight file copies between systems.