If I'm on a week long or more pack, I'll shave. It gets itchy after a week and I find trying to sleep on the growing beard is a bit irritating. I also get pimply under the hair from ingrowns. So, I take a disposable, and a chunk of shaving soap I buy just for this. I get my soap from an ebay store called Susies Bubbles and Squeak. Best shaving soap ever. Pack a lightweight, cheap brush and I'm good. All together it weighs about 7 ounces and I don't really notice it.

Of course if it's less than say 4 days, I just let it grow.