I hate the three man rush, too. And I totally get what you're saying about giving up the quick score...I mean that's one of the main premises behind playing a prevent...make them take time off the clock. That said, when the prevent leads to a relatively quick score (as I'v seen happen many times), then someone really needs to examine said "prevent" defense. Like you stated though, if a team is up by a good margin (three possessions), then by all means play it. Just make them eat up some time/burn TO's in the process.