I was a voluteer during college. Obviously I would not have my pager on during class or during work (worked part-time all through college). All other times, I would have it on.

Obviously, if everyone was like that, there wouldn't be nearly enough people available. But, there were a lot of people who worked at jobs nearby that could leave. Lots of part-time people. Etc...

Somehow, it just all works. May not be an ideal situation, but we certainly had coverage...