Having so many copies was expensive advice perhaps 20 years ago, but now it makes a lot of sense.
Drive capacities have increased so much that, unless you're trying to create your own copy of Megaupload or The Pirate Bay, you can easily afford to maintain many duplicates of any data you care about. The real problem is bit rot. How can you be sure that random corruptions that might accumulate over the years don't cause you to lose an important file or two or two thousand?
A service like crashplan or backblaze should largely take care of that for you. Unlimited incremental backups for a fixed monthly fee. If you discover a file has been corrupted, you just go back in the incremental versions until you get to a good copy. If $5/month is still too much, you can even point it at one of your own machines. You still get the incremental backups; you just have to provide the storage space.
Either way, the key is not just to have multiple copies of the most recent iteration of a file, but to have an automated system of archiving past versions - of everything - as well.
Drive capacities have increased so much that, unless you're trying to create your own copy of Megaupload or The Pirate Bay, you can easily afford to maintain many duplicates of any data you care about. The real problem is bit rot. How can you be sure that random corruptions that might accumulate over the years don't cause you to lose an important file or two or two thousand?