A lot of excellent points of view have been offered here on this. I have to say that I can see merit in most all of them, dependent on your personal situation/expectation.
I have CTIS on 2 of my trucks. The HET and the PLS both have it - and they both work great (thank goodness). I did do a little surfing/research on here on the CTIS subject when they first started hitting the market. Unfortunately for this thread, from what I understand the "heavy" Oshkosh trucks might have a somewhat different system than the 2-1/2 and 5 tons. Maybe the differences have more to do with the axle seals and such and not so much about the rest of the system. But the one thing that I did end up taking note of in my "preventative maintenance" searching was a reasonable and logical comment offered by one member (forgive my memory) that one of the main causes of failure to the system(s) is (internal) contamination. It was mentioned that deliberate attention should be given to the "air dryer" systems on trucks with CTIS as water and oil contamination of the compressed air which is then used to operate the system can be an issue. It follows that these types of contamination can cause failures of the seals, etc., amongst other things. I have yet to service the systems on the HET as it only has 500 miles on it, but when I first got the PLS and had it gone through at a local heavy truck shop, I was adamant about having the three tandem air dryers serviced. PM, PM, PM. Come to think about it, it is not much different than our civy vehicles out there now. All of the "toys" and "systems" on them usually operate pretty good, as long as we follow the "recommended service intervals" and stuff. They operate well, but might need more "pampering" than us somewhat older folks who grew up on 350 V8's, mechanical fuel pumps, carberators w/ floats and needle valves, and only 3 sizes of headlight bulbs, might be used to!