Have you considered an online backup service like carbonite?
There are others, maybe better organized, but this offers unlimited data for an ok price.
Deleted files are still "saved" online for a month or so and if you realize your mistake you can re-download them on your local disks.
Depending on your shooting style, how good you are to edit down your photo sessions (aka delete some of the 1million shots of the same thing you got if they don't worth it) and how many MP your camera produces, 1TB might fill pretty fast.
My backup of choice is on external HDDs for sessions that were done with PP, and I use Sugarsync
($5 a month) for the unprocessed stuff that are only in my local HDD.