Yes, as anyone who bothers to read data sheets would be aware. If it's funny
to ask the original poster a Q in order to gather information needed to
provide a useful, helpful reply....then it's also a bit funny thatI have
units in the field for over 15 years with original optos and no noticable
performance degradation. I guess it all depends on part selection and
application knowledge & experience.
While it is true that an opto emitter rated and run at 20mA will have a much
shorter useful life (also to be determined by application) the same will run
for a long, long time at 3 or 4 mA and there are many ways to get back the
high CTR & fast response as if it were run at 20.

My question was originally intended to flush out application reasons that
optos were a no-no in this project....Which apparently has yet to be shared
with the list. Is the reason cost, lack of familiarity with opto's, product
longevity, or whatever???

There is major short-sightedness in the inclusion or exclusion of a single
device or technolgy in a design based on a single parameter and an opinion
based on limited info - especially since that parameter or quality may or
may not be a real concern in the specific real-world application.

> A bit of a funny comment, since opto-isolators are one of the few
> solid-state components for which aging is an important engineering
> consideration.

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