[aes256]

Notwithstanding something exceptionally rare, why the need to back up FLACs on S3?

I back up my music collection locally, and I have double-redundancy of sorts (it's backed up to a RAID 5 array on a file server, so in theory it could withstand the failure of the original drive and one of the back up drives), but if worst comes to worst I could just acquire everything again.

With a couple of exceptions they're just lossless copies of widely available music recordings...

[justincormack]

Are you suggesting backing them up on pirate music sites?

[aes256]

Not advocating copyright infringement, nor was I suggesting that in particular.

That would be a viable back up strategy, though. Have a rare copy of a recording? Make it widely available, then if your copy is destroyed, the odds of you being able to acquire an identical copy again are much improved.