I was just about to post about this. I did a 10 hour drive today, and my empeg still went over 55C. It seemed to stabalize at about 57C, but the fan didn't work as well as i'd have hoped in car. So the empeg spent most of the trip 2 degrees over spec.
Which reminds me... Mark... Is there any way you could have some sort of notification in Hijack if the fan is ON? It's pretty much impossible for me to tell if it's even working while driving... Maybe just a flashing F in the temp window or something?