How many miles have you towed in one day?

We try not to drive at night, expecially thru construction areas but often find ourselves on the road just before daybreak. We eat early and don't resume driving until the next morning. A nice day with sights on the way would be 250 miles, destination driving perhaps 350 miles per day. Have done 450 miles per day for an unplanned "have to be there on time" event.
BTW, we split the driving 60/40....and I find I have to fight for every minute of my 40%. She likes driving that much.