The longest non stop I've driven A Morgan for is 36 hours ish including food and fuel stops, but I was only 17 then, been in the car for 20 + hours many times thow and never been a problem.
Just treat it like any other car, I would think you want to drive for about 3-4 hours before having a rest for 30 mins to an hour, they prefer A and B roads to motorways so take that into account when planning your route.
And if you have the oiler system swapped for grease nipples take a grease gun with you if your going that far.
