Here's what I'm thinking: If the law of diminishing returns applies to continuous process improvement efforts, that means CPI provides the biggest benefit during its initial phase, and provides smaller and smaller benefits over time. That might mean it's a good short-term strategy, but somewhat weak over the long-term... so maybe the "continuous" part is of dubious value?
I've only just started thinking about it in these terms. I suspect I'm on the right track, but I might be missing something here. I sincerely want to hear from people with CPI experience & insight - and my first round of google searches turned up precious little on the topic.