Do you rely on RAID as your NAS backup?

Again, RAID is not a backup.  It can be destroyed by controller failure, virus, voltage spike, bug in OS or controller software etc.    If you use Crashplan you can use it with single drive as well.  Crashplan is your backup - not RAID.
In addition, as Al mentioned, recovery can take forever.  Also, companies have system problems, go out of business, change rules etc.  I would rather trust my plain backup drive.  Unpowered drives in storage tend not to fail.  In addition simple solutions are always the best  - read this link:

http://jeffreydonenfeld.com/blog/2011/12/crashplan-online-backup-lost-my-entire-backup-archive/

Ozzy, I also keep my "source" drive ON but it goes into sleep mode. Check "Power Options".  In Windows 7 hard disk timeout is in "Advanced Settings".