That's pretty much how I use it as well, at camp and away from the truck, talk through the truck on the HT. I set up the HT frequency on UHF with a tone so that it wont open and transmit as cross band without it.Crossband repeat is a touchy subject in the HAM world. There has been a lot of debate about if it is or isn't legal.
I have found it useful when I got to camp early and wanted to hike. I set up my cross band radio with whatever frequency the group was using then cross banded to my HT. The thing to watch is not to interfere with local repeaters or commonly used frequencies on the repeated (HT in this example) side.