Most of the mods have day jobs, and most if not all are in North American time zones. Add in family responsibilities, school, etc, and you're asking a lot of volunteers to agree to be here around the clock.

You can find them if you check the "who's online" feature. They don't "have" to be anywhere, such as in chat, and all are PC members themselves -- you might find them posting about their own issues! And you can always PM one or all.