Trip of a lifetime? Take a spare camera.
Jamie, AKA Travel Savvy Mom, suggested I file this under "lessons learned the hard way:"
For reasons I don't pretend to understand, cameras always seem to go on vacation when you're on vacation. Not long ago (in famously photogenic Seville) I looked through my viewfinder, zoomed in on my family, pushed the shutter button, and...nothing happened. Luckily we were in Spain and not Papua New Guinea, so I was able buy a replacement without too much trouble. The worst part? We had a spare camera at home.
If you're taking the trip of a lifetime always, always bring a second camera.
This story brings to mind the magnificent photos I took at Glastonbury Abbey -- the late afternoon light was golden -- until I realized, as we were leaving, there was no film in the camera. (Remember film? The stuff you used to load in your camera before they went all digital?) Still breaks my heart.
Related: All manner of travel hacks in the Travel/Going Out archive