How to use the 2 cards in a D800

I'm trying to decide how to use the second card on my D800. The CF card is always set for RAW. For months, I've used the SD card for medium quality jpegs. However, even though I download them into Lightroom 4, I have yet to use one. I always simply work with the RAW files - sometimes saving high resolution files for prints, sometimes downsizing to simple e-mail sizes. My original idea was I'd use the jpegs for easy emails. But I don't like to output any images which haven't had full post-processing--even for emails.

I'm a fairly particular amateur. I mainly shoot landscape, wildlife and travel photography.

Am I wasting my second card slot? Should I use it for higher quality backups or overflow. I am getting ready to spend a week shooting in Yellowstone this winter. What do you folks recommend?

Also, if I do change how the second card is used, do I need to take that into account when buying cards? Presently I use all Lexar pro 800x CF cards. Do I need to match that speed in the SD cards?

Thanks,

Greg