I tend to think that a cracked DPF is bad in the long run. The system relies on sensors and if the DPF is cracked and letting out soot then it may not regenerate as it should (thinking things are running cleaner than they are) and this would cause the system to ultimately clog up and back up into the turbo and such...

 

Why would it clog up? The soot is being expelled through the crack.
More cracks = more expelled soot = less regens = less fuel being used.
Almost like a DPF delete!

 

The re-gen process relies on delta P across the filter (pressure drop) to determine the soot load (grams) to keep the DPF at a certain level. If the crack fools the ECM into thinking there is less dP it may not regen and clean it as it should.

 

My Jeep regens weather it needs it or not every 750 miles, so I'm sure that your trucks have a mile schedule also.

 

That is pretty much exactly it and put better that I had stated. The DPF will be clogging (while still expelling soot) and the system won't regenerate properly and therefore causing damage to parts upstream.

I have not heard of or seen proof that the system regens on any timer. Even so, the system with a cracked DPF could still clog up faster than a timed regeneration could handle.

Soot on the tailpipe of what should be a properly working system is not sustainable...