If?Have you seen the other thread, Jon?
It seems as though he's going to burst-mode every single image he takes! *laugh*
If you burst-mode everything (as your other thread suggests) then as much as you possibly can handle!
My drives are as follows :
1 x 320GB
1 x 500GB
1 x 1TB
Shortly to have another 500GB drive.
The laptop drive is 500GB (thinking about upgrading to a 1TB).
The answer to your question depends on how much RAW/JPG you capture and how much video you think you'll take.
Mark