I'm looking to buy a second camera card for my D5000, as a "just in case" my current one fills up while I'm on vacation next week. When I purchased my camera, the lady had me buy the really expensive SD card with the fast download time, etc. If I'm just using it as a backup card, is a higher end expensive one really that important? Or do you think I'd be okay getting the less expensive ones from Walmart or Target? (They have an 8GB card for around $30, I think). What's the difference between the more/less expensive camera cards - is there a difference in quality, or just download time? Thanks for any advice!