How to tell if main bearings and rod bearings are need of replacement

[Jon]

Last night someone here spoke about replacing there rod and main
bearings at about 150,000 miles and I was wondering how can you tell
that this needs to be done? Is there some type of inspection you can
do without removing the pan? And what happens if you don't? Seems to
me that if one was to treat there engine with a little respect of
sorts this should not be a problem that would creep up till you had
way over 250,000 miles or allot more. These coaches are suppose to be
million mile rides but it sure seems that allot of people here have
not even got that close with there engines as far as that goes. Any
answers please?

Jon
Rebel Bird