Jeanne, we also use bark for our larger snakes for the same reasons. (Our hatchlings are on aspen.)
Raj, whenever we find urates or feces, we scoop out a rather large area of bark. If there's any wetness underneath, it's cleaned up and dried, then the area is replaced with clean bark. Once a month, we clean and disinfect the entire cage and replace all the bark. So far, we've had no problems. You do have to be more diligent with loose substrates, so I guess it all depends on what's important to you. I don't think there's any "right" or "wrong" when it comes to substrates (other than those that are potentially toxic, of course) as long as you provide your herp with a clean environment.