Used 2011 F350 6.7. Do I need to purchase warranty?

It is amazing that folks need a button to play with to make it real for them. I have towed a medium size travel trailer all over the country preferring roads other than interstates and never overused the service brakes. You don’t need to drag the rear tires to have an acceptable amount of control. If one would just know to use tow/haul and apply the brakes to slow just a bit, the truck will handle it from there.