I do agree with you to some extent java. Even I replaced my 100K plugs after 5 years in a windstar at 60K mi.
Those plugs did not look too bad after all that time, btw. But in the case of plugs the issue is not that the plugs won't last it is that they may not come out after say 8-10 years and 100K mi.
There is somewhat of a difference between extending service intervals and eliminating them altogether. I am guessing mfr could even say you only need to change oil every 10,000 mi and probably get away with it as any problems would not show up until long after warranty ends in most cases. Don't think they would want to try I was looking around the web on transmission fluid changes in general and apparently some mfrs are now saying 100K mi or no change at all unless fluid is brown or something like that.
In the case of my atx windstar I change fluid every 30K as mfr recommends. I never heard of changing brake fluid or mtx fluid until recently (and I have been around a while).
Don't misunderstand my questioning of this stuff is not meant to dispute the advisability of doing it, I am just some idiot trying to understand reasoning for it. In the case of atx fluid my understanding is the high temps cause the fluid to break down...just like engine oil will. I don't think that this reasoning would apply to mtx fluid (I could be wrong...its not like I know anything about cars) or especially to brake fluid or power steering fluid for that matter.
