Not sure about that. I've had mudflaps on every truck I've owned and that's been many being 53. I live in New England and do a decent amount of off-roading with a mix of mountains and beach and have yet to break one. In fairness I wouldn't consider myself a "hardcore four wheeler".
Guess it really depends on what you do mostly. I never had much of a problem with the four foot bed on my previous Sport Tracs with what I do with beds.