For a short 2- or 3-day tour, you could overinflate your tires slightly. If your ideal pressure is 100 psi, start at 110-115 psi on day 1 and you will be at 90-95 psi on day 3. Of course, it doesn't help if you get a flat tire.

Thicker tubes loose air less rapidly than thin lightweight ones.

Finally, one of the best investments I made was a Topeak Road Morph. You put it on the ground, install the chuck, and it's fairly easy to pump the tire to full pressure without fear of breaking a valve or injuring one's arms.