I heard that tape drives have the best cost to storage ratio, makes them great for backups. I also heard that cd are the only media resistant to magnetic impulses (well, printed books are also resistant). I also heard that cd slowly rot away, that they aren't intended to last for longer than 10 years.

Standard approach is to have lossy audio to actually listen to, and lossless audio for archival purposes. I doubt aac vs flac is actually noticeable.