If you like to watch TV and DVDs while "off grid" I recommend getting a TV/DVD combo that runs on 12 volts DC. You don't have to buy a TV from a 12 volt specialty supplier. We bought a 19" Insignia HDTV/DVD combo unit from Best Buy that runs on 12 volts DC. (Disclaimer - I don't work for Best Buy and I'm sure there are other great 12 volt DC TV/DVD options out there. Shop around!)
But, the Insignia TV/DVD isn't sold as a unit that runs on 12 volts. Instead, it plugs into a 110v outlet, with a power cord that has a transformer supplying 12 volts to the TV. (That's that big black box on the power cord.) Look for TVs with a transformer powering them. You have to look at the spec sheets (or peer at the back of the display TVs, annoying the sales clerks) to find out what voltage the TVs actually utilize. A lot of 19" TVs run on 12 volts DC these days. The 19" Insignia TV/DVD I bought is rated at only 3 watts. That's not a lot of draw, so we could easily watch a movie or a broadcast without draining down our batteries too much.
I headed over to Radio Shack, where I picked up a fused cigarette lighter plug and a "K" plug adapter that fit the TV's power input. (I actually had to convince the clerk that I could power a TV from a 12 volt power supply. Sheesh--Who do they hire these days? But, I digress.) I soldered the K connector to the plug (observing +/- polarity) and the TV/DVD is good to go.
I started this whole project because our Winnebago has 12 volt power supplies at the bedroom TV shelf and on the outside "entertainment center." (A marine AM/FM Cassette player and two speakers--state of the art in 1999!) So, the TV plugs right in outside and in the bedroom. Granted, we can't watch the 32" main TV on nights when we dry camp, but we consider that any TV or DVD viewing while off the grid is a pretty good deal.
That's my 2 cents for enhancing/extending a dry camping excursion. As others have said, how long your batteries will last is something you just have to find out from experience. Good luck to you in your dry camping adventures!