I realize on the Internet you can't often tell sarcasm. I was exaggerating about being able to last 2 days past the warranty. But I can tell you from experience that guys who fully load and especially overload there trucks on a daily basis have much more money rapped up in repairs then people who typically tow or haul at or well bellow the factory rating.

I have been in the tire/repair business for over 10 years now and regularly see heavy and over loaded pick up trucks. We have put plenty of transitions, spring hangers, and other parts on trucks due to the excessive weight. Often it is the same guys with the same trucks getting the same things replaced. Like you said the "factory rating" is given with a large air of caution so that the dealers aren't constantly replacing parts.

Now to answer the modified question of the OP a truck can damn near pull anything you put behind it. I live where it is flat so hills and mountains don't play any roll around hear. My 1500 Tahoe has had around 12,000 behind it and did a great job. It certainly could do more but it was a one time thing. Pulled the load to and from a house to use the equipment. I am sure if I put 12,000 behind on a regular basis the truck wouldn't last too long but I am not sure the factory ratting on my truck to be honest.