I monitor mine on my Edge CTS Insight. I check at each oil change the injector rates....to be between -4.0 and 4.0. Mine stay at -1.0 - 1.0 with the exception of a single injector, it stay at -2.5.
There are all kinds of ways to watch for injector failure...I send in an oil sample each change and scan over it for fuel in the oil. I have heard people say rough idle, loping when cold, lack of acceleration, etc....
You can do an injector cleaning in a couple hours. Getting a gallon of diesel , injector cleaner, 6 feet of fuel hose and a 6 pack of beer. The directions are on the duramaxforum, but it is super easy...gets done once a year for me.
Cale
TV: 2015 6.7 F350 CC LB 4x4 DRW with 14k GVWR option (4.3 gear), 98 gallon aux tank installed by Transfer Flow
New: 2014 Voltage 3950
Traded: 2014 Outback 323BH
Still Have: 2007 Fleetwood Nitrous 23ft Toy Hauler