Your coolant temp is what I would worry about! I think I would have it flow tested flushed or just buy a new one! Where do you have your EG thermocouple mounted? If it's in the exhaust manifold your EG temps are fine. If it's mounted just in front of the turbo then it's at the max and if behind your running way to hot.
As for worrying about shutting down don't, unless your running hard and pull into a rest stop don't worry. If pulling off the interstate for fuel by time you get into the station the turbo will have cooled down enough to shut it down. Myself I just left the truck run during the fuel up.
BTW I ran full syn oil from the 500 mile mark until i sold the truck with 150K on her.
Don