Okay...I see your concern. Certainly, there are cams available (for more popular engines) which are designed for high-RPM horsepower on overreved and/or overboosted engines which can hardly idle straight and probably don't last as long as a Yugo. But in the case of these comparatively mild cams for the 4ZE1, I just don't see any longevity issues other than the point Chase made earlier, about how you treat your engine. If you throw in a new cam and drive it like you stole it, you're bound to run into longevity issues (well, even without the new cam the same thing would apply). "Valve float" would be much easier to achieve if you're pushing the rpms and you've got a performance cam. And that would be less than ideal.
So, let's assume that you drive normally (if we can agree on what "normal" is). For example, my 2.6 rarely exceeds 3500 rpm, and *almost* never exceeds 4000. If I had a "performance" cam, all it would be doing is opening the valves a little longer and/or a little further to allow more air/fuel mixture in. Not so much more that the computer and injectors can't keep up with the increase. And the mixture is not being "crammed" into the combustion chambers by forced induction. It's just allowing a little more to come in.
As far as emissions go, it's increasing the total amount of exhaust gases (because it's allowing more air/fuel into the combustion chambers), but it's not doing anything to increase the concentration of harmful pollutants found in those exhaust gases. Same thing with headers, really...you still have "x" ppm of any given pollutant, but more exhaust in total. Which is why people in CA have passed smog inspection with headers and/or a Delta/Calmini cam...the bad stuff is measured in ppm without regard for any grand total. Along the same lines, but at the opposite end of the spectrum...some redneck tweaker once told me to cut a hole in the exhaust pipe of a car I had that wouldn't pass smog. That wouldn't have done anything to affect the sniffer test because it's measuring parts per million, regardless of how many parts there are in total.
Well, that's all just my opinion anyways...that if you drive "normally" with a Delta/Calmini cam, you won't run into any longevity issues. I understand and respect your concerns, but I don't happen to share them on this issue.

oh...one more thing. Your example of the Honda motorbike engine...look at the significant difference in those numbers, is one engine "less durable" than the other?
I'd venture to say no, unless it's abused regularly.

It's never personal, bro. And I'm 32 next month.
As always: <img src="/forums/images/graemlins/cheers.gif" alt="" />
Phil