What's the longest/heaviest you would tow with a 1/2 ton?

2012 F150 HD 3.5L Ecoboost. Towed a little under 10k from south Texas to different parts of Utah twice. Not once did I have a problem keeping speed up or down the mountain roads. Never felt any brake fade and had plenty of power to pass when needed. I would not hesitate to do it again if I still had the truck.

Most have never even towed anything heavy with a modern half ton that was appropriately configured for the weight so they really don't have the experience to give an opinion.