Thanks everyone for all the reassurances! In the end, it was a pretty uneventful drive, though, we woke up far too early in the morning.....went to bed too early, and am now up too early!
I think the most I have put a truck like this through before has been about 350 miles in a day, and that was part of a trip from Spain to the UK, via France, Italy, Switzerland, Germany and the Netherlands. Each part was in small segments of about 250 miles, sometimes more, sometimes less, and the longest individual trip was about 350 miles - overall, we did about 2.500 miles, but it was over a month!....and far more interesting than the trip we just completed!
1993 NAS 110 300tdi conversion
1985 90 300 tdi (from Italy)
1985 90 prototype
1983 S3 88" Safari SW