Tundra owner here and the downside to long distance towing with the Tundra is its "short legs" meaning it can comfortably go about 200 miles towing with the 26 gal tank. It is normally not an issue for us but has been a few times and I've considered carrying 5 gallons of gas just in case. On the other hand, I don't like to drive over 200 miles without taking a break anyway, there just needs to be gas nearby if I stretch it that far.
BTW, I know my Tundra can go at least 10 miles towing when the DIC indicates 0 miles of range left. Don't ask me how I learned that.