I use an 8 gb storage card and I can save an awful lot of pictures in RAW and JPG before having to delete anything. But alas...while shooting my mom and dad's 50th anniversary last weekend...right when I was about to get that 'shot of a lifetime' the card filled up and I lost the shot. I'm a bit of a pack rat and forget to delete RAWs of shots I don't particulary care for. I had shots of my mother in law's Halloween pumpkins on that card. LOL
Fortunately I download pics right after shooting them so I did not lose anything when I had to do a quick delete on the camera. I also make a copy of JPGs for archival purpose so that if I do degrade a JPG over time I can always do a DOS level copy/paste of the original JPG without opening it.