A diesel shop in town can do an “in truck” injector test for $75. I think they just look at metrics from the OBDII. Is that a worth while test in your opinion?
Yes, it's worth it, IMO.
You want to know balance rates and return rates. If all in spec, I wouldn't touch 'em. Your 2 micron filter will likely keep them alive for a while longer.
That said, 200k miles, OE crappy filtration and original injectors in a CR Cummins are almost mutually exclusive. I wouldn't doubt for a second that they've maybe been replaced in the past.
"Some" injectors have catastrophic failures that can lead to the bad things happening to the engine. But most just wear out, slowly. Like our old 07, started/ran just fine. At about 120k miles I put them to an extreme test, truck was cold soaked at almost -30F for a few days and wouldn't start. Had enough cranking rpms (felt like it), but the return rate on 2 of them was just too high to build enough pressure to trigger the ECM to fire them at that temperature. Brought it back to town, 6 hours in the garage with some heat, and it fired up no problem. No smoke, no mis-firing, drove it for another month or 2, just plugged it in at night (Alaska, winter). Had a shop do a kill test, passed, and balance/return rates and return rates were just a bit out of spec on 2.
If we'd still been in Seattle, no telling how much longer they'd have lasted.
That said, if you suspect they were replaced anytime in recent miles with unknown re-mans, I'd change for peace of mind.