This will start a big debate. I've done a lot of research and have almost 300k miles of LML experience as well as LML friends too so here's my opinion.
General concensus seems to be that the CP4 was designed for the European market where they have better fuel and apparently has not been as big an issue over there as it is here with GM.
The CP4 is not as reliable or durable a pump as the CP3 that was used up through 2010. Ford has used the CP4 as well with a little better results but they also used it in tandem with a lift pump.
Many guys get many trouble free miles from the CP4, however, many have had premature failures. I put a FASS pump on mine when I bought it at 98k miles. I know several guys that run either a FASS or Airdog with good results. Some guys will say these pumps may actually do more harm than good and actually just promote a simple lift pump. I got 244k miles out of mine without failure but when I had to perform some heavy maintenance on mine last summer, I replaced the pump, injectors and rails at the same time.
My most up to date theory is that CP4 life corresponds to the fuel you're feeding it. Where I live in the Midwest like most of the rest of the nation now, about all you find at the pump is B5-B20 biodiesel, which is arguably about the best thing you can do for your fuel system. Bio blends at only about 2% provide more lubricity for your fuel system than any additive you can dump in your tank. So the guys that are still running bone stock without additives and achieved many trouble free miles are probably running almost solely on bio fuel.
I wouldn't fuel anywhere that I was afraid of fuel quality or contaminants, especially water. Most sediment type contaminants can be removed by filtration but whether or not you're getting most of the water out of your fuel could be another story. It seems to be a little tricky to trap all of it. Many guys, myself included, report rarely ever finding much if any water when we open the drains. Some additives try to take it on through the system while some try to take water out the drain, emulsifiers vs demulsifiers.
Bottom line, if you ensure a good steady supply of clean fuel to your pump, without contaminants, you probably have a good shot of having a happy CP4 pump for many miles. If you elect to remain stock, I'd spring for the best fuel filter you can find, probably AC Delco, change it religiously and always try to buy top quality fuel from a high volume source. But if you want to hedge your bets, positive pressure to the CP4, added filtration and fuel additives all seem to be good investments.
Schaefers has good stuff but if you want to see how many of the top fuel additives stack up against each other, refer to the Arlen Spicer diesel fuel lubricity additives study results. It's several years old now but still good reference. The only bogey now is if one or more of the additive companies has changed formulation. You would hope if they have that the change was an improvement.
That's just my opinion. I could be wrong