STORAGE for Pros with large MPs and lots of images.

There comes a time with 21 MP cameras, RAW images, huge psd files from lots of editing that offline storage must be used. I have 1.5TB of RAID on my computer and DVD drives and a 1.5TB server for backingup to a remote location .... but I'm still running out of room and need to archive to something long term. JPGs I'm planning on keeping on my computer in order to catelog eveything although I may shrink them, but I need to start archiving RAWs and finals for clients. I want to keep 2 copies of everything for safe keeping. I love it if BR DVDs higher capacity format was ready for use and cheaper but its not. So I think the only alternative is portable hardrives. Any thoughts? I worried about long term shelf life of this type of storage. I can pickup 500GB USB2 Lacie drives for about $100 bucks, but which ones have the better archival quality?

It seems like everyone has a slightley different solution for this. I right now use a 500gig drive but need to be upgrading to more storage solutions. I have friends that have tons of 500gig hard drives. Just keep adding more hard drives two at a time when you need them. It is kind of pricy but really it seems to be the only way to go.

I was looking into this http://www.drobo.com/p​roducts_drobo.html, which really great for storage, but then I found out that once you fill up a disk and remove it you can not put it back or else the disk is formatted, if you needed to get pics from a certain drive you would have to hook it up to an external device, but the concept seems good.

80gb of CF cards on the move. Not cheap nor terribly expensive, but far more reliable than 2.5" HDDs.

At home 2x Seagate 750gb FreeAgents. One is used to backup my laptop and other stuff, and the other is a photolibrary. Very well priced and more storage than I need really.

Protected RAID array that copies to second RAID array on local network, then two offsite USB drives of which one remains offsite. All copying handled by robocopy.

Also to thin things out I copy all processed RAW images to two DVD's, each of a differennt brand in case their are batch issues (lost a whole pile of CDR's a few years back to a bad batch, and they were a good brand too!). Started keeping the RAW files on a cheap USB drive as well for quick access.