Well - what Crganski and DeMaestro said. Bounce rate means really that the user only hit the site once. So in general you can't measure how long the user engaged with the site. That's a real problem, but couldn't someone write a script that refreshed every now and then? I'm no programmer, but I do see pages that do this for other reasons. Presumably this could be done, but it would really need to be built into the analytics system being used otherwise it's really not helping man nor beast.