i think it depends on how you're traveling and to where (space to work once you're there). i can't stand waiting for people, but frequently find myself with anywhere from 15 minutes to 2 hours on my hands. i always have reading material and a cigar box full of parts to be cleaned up with me. Optivisor, clip on book light (battery powered), xacto, 3 grits of sanding sticks & wet/ dry paper, razor saw w/ wirenut handle, 3 shaped needle files. i think that's about it. i don't want to build, just do the prep work.
your conditions may vary.