We don't list mirrors that has been offline for longer than 24 hours unless they're marked official. The site you mentioned is listing them for 72 hours. But no history is kept beyond that. We think 24 hours is enough for a mirror to come back alive.
@jpoker23 The trustdb could be used to report the incident stating the seller's username. The idea behind this is that future buyers can look up the seller's handle across multiple markets and get a detailed report of either successful or unsuccessful purchases. Thus vendor should be interested in having a perfect score replying to each issue. If you have suggestions to enhance this mechanism I am all open to discuss it.