W_D's account illustrates why it's a good idea to plan a layover day or two into your backpacking schedule.

I remember one summer horsepacking with my parents (I was about 14 or so) and my mother kept getting bouts of GI illness that laid her low for a day or two at a time. When we got home, she got a few more. She finally went to the doctor and ended up having an appendectomy. My father and I were thankful that she didn't get an acute attack while we were out in the mountains several days' ride from help!

Acute appendicitis (as opposed to the chronic kind my mother had) is a case in which a PLB would be a good thing to have.