Nikon D300 is 12mpx ? So the Raw should be around 15MB which should let you store over 2000 photo on a 32GB card. That's a good number already before coming back to unload on the computer. And 32GB CF Card are cheap also ($30) if you need more.
My 32GB card will only hold 1100 images when empty, so will just have to have a few cards spare when I go out shooting timelapse.