Short trips will kill any exhaust except the high $$ stainless. The only reason the exhaust is lasting 10 or more years is because the newer factory installed pipes are thicker then they used to be.

The combustion process creates acid, and it takes 30 minutes of running time AFTER the motor reaches operating temp, to remove the acid from the exhaust. If your not eliminating that acid, your exhaust is getting eaten from the inside out. The exhaust joints and flanges will be the first place for the damage to show up.

Then we can add the modern ice melt many highway departments are dumping on the roads that is more corrosive then salt is, so the outside can be eaten away as well. Gene