Regen or Regeneration is a process that burns soot off the DPF filter. Without this, eventually the engine will shut down. It is usually an automatic process, that will occur every 300 miles or so. But, when you do a lot of stop and start local driving, it may have to be done manually by a mechanic.
Over 50 degrees-2 minutes, 0-50 degrees- 3 to 5 minutes, and below 0- 7 minutes. That is the basic standard of idle before driving. You do not need to idle it before shutting it down.
Shorter trips do not allow the engine to warm up appropriately, and can cause carbon buildup. To avoid this, it is recommended 15-20 minutes of loaded running, and at least 1 hour of straight highway driving per month, to keep a truck in shape.
Peterbilt engines are extremely well built. With proper maintenance, they seem to go on forever without major problems. Also, those who haul heavy loads, or livestock, love the long nose of the Peterbilt. With a longer wheelbase, the truck and trailer have much more stability.
"I have found that being honest is the best technique I can use. Right up front, tell people what you're trying to accomplish and what you're willing to sacrifice to accomplish it. - Lee Iacocca