Towing a Dodge Dakota four on the ground

I tow a 2006 Dakota and have never disconnected the battery and this only caused me a problem one time, and that was a cross country trip. I towed it 700 miles in one day and at the end of the day I started the truck and ran the engine for about five minutes. Since it started fine I thought I was good to go. I did 700 miles the next day and when I stopped that night, the battery was dead in the truck. But I always carry jumper cables so I just jumped it from the motorhome and all was fine. But I've done other trips of 500 miles in a day with no problem. I think if I had let it idle for an hour on that first trip I wouldn't have had any problem.