The HEUI system is often misunderstood, and susceptible to many malodies. When properly maintained, it's a very good system. Unfortunatly, because people don't understand it's full operational parameters, things are often misdiagnosed, and therefore blamed.
I'm sure that truly neglected OCIs have resulted in poor performance and injector issues; the system of course does run on oil-over-fuel. However, the is only part of the systems. Hydraulic Electric Unit Injection; the name says it all. The hydraulic is only part of the system, and yet people ignore the other very important part.
Many times the poor injector performance (slow to start, sluggish acceleration, poor fuel econony) is a result of the FCIM going bad. And many times the root cause of that is the battery voltage. This is information that has been around for many years now, but it's easier for some "shade tree" guys to blame the easy stuff; blame the oil. I'm not calling anyone out here, but I'm pointing this out because some would easily rush to judgement without being able to articulate the full circumstances around HEUI. When battery voltage is weak and/or charging system amperage cannot keep up with demand, the voltage to the FCIM drops and that in turn causes the injector voltage to drop, resulting in sluggish response and/or outright injector failures. Or, quite often, the FCIM itself will eventually fail. Most often, we think of electronic failures as "all or nothing" when it just "dies" a sudden death. But the FCIM more often degrades slowly, sometime so slowly that it's not noticible to the driver over many, many months.
There is a reasonably articulate article in the new Diesel Power magazine; it's a decent read about this very topic. It rightly points out that weak batteries are the root cause of the FCIM degredation, and even after you replace the batteries, the problem lingers because the FCIM is compromised. People will replace the batteries, and then blame the only thing that pops into their head; blame the oil.
I'm not saying that is the case in all PSDs. I'm just pointing out that "extended OCIs" (lube related issues) are not the only cause of injection issues with HEUI. In fact, if the oil change extension is well controlled (solid UOA parameters, bypass filtration, etc) it's more likely an issue with the FCIM.