A timely reminder, we have a friend who didnt take the advice given to him.
They have a Mazda BT50 with the 3.0 TD with the 5 speed automatic gear box, its now in a small country town with a cooked grearbox. All because he was towing his 24' caravan in DRIVE.
If you insist in towing in drive you may get away with it for years, but then it might bite you on the ar$e one day in the middle of nowhere and looking at a expensive repair bill.
Oh they only travelled about 30k on the day it died.