I agree with rost495 about having a good backup. The new GPS units are really amazing especially if you have mapping. Over time you have to remember that all things electronic can fail. I too carry spare batteries in a sealed 4 pack and a couple of compasses. When I am in big country I use the compass and the GPS unit together to periodically check on my posiition reletive to the truck. If you are 10 miles in on a dirt road and parked at the end you don't want to miss the truck at last light.