ditto on the Trojans. When I first got my trailer, I bought a brand new middle of the road 12V deep cycle. Camped in weather with highs of 10 deg celcius down to about -2 at night. With the furnace cycling continuously, battery was toast in 16 hours. Now with the two 6V Trojans, I can go for about 84 hours under similar conditions.
As far as using in our trucks goes, keep in mind that cranking power and amp-hours do not necessarily go hand in hand. I'll stick with a good set of 12V's in the truck.
Dave