If done properly there are two positve power on your truck. One runs the running lights and the other goes to a battery, which is normally used for emergency "brake away" brakes. A lot of travel trailers just use a large deep cycle battery instead of th little "break away" battery. So you can run accessories like Interior lights, electric jacks, awnings or even the blower on a propane furnace. If one was to want to camp in a trailer in so get month you should look into this set up.
LEDs are perfect for campo g on battery. The ones off of pirate are perfect. I believe his name is bigred something or another. I bought like 50 last year and put them in a travel trailer. Lights for 2 days on a battery. Or through a solar panel on roof then you don't have to worry about maintaining your battery and it's always ready to go.