You are right in that DVD players are different in this regard, because of
the high rotational speed of the disc, but then I had already explained
that
in my previous post. For sure, on these lasers, film contamination *is*
the
most likely cause of a 'dirty' lens rather than loose dust, but as I also
explained, because of the semi-open nature of the optics, the vapour-laden
air will get inside and condense out to coat the optics - including the
underside of the lens - resulting in compromised performance, even if the
lens upper surface is restored to a Windex sparkle.

As to why you have not had a problem with your optical players, I think
you
answered your own observation. You are not a smoker, and you don't live in
a
particularly dusty environment. Of course you are not alone in this, and I
guess many thousands of people enjoy similar trouble-free performance from
their players, but many others do smoke and do live in a ****-hole, and
they
are the ones whose players we see in the world of service. Another factor
is
the type of player. I think that from what you have said in the past, you
tend to go for more up-market equipment. Generally, CD and DVD players
that
fall into this category, have closed-in unvented cabinets. Basically,
except
through the tray opening, there is nowhere for dust and other airborne
contaminants to get inside. However, that's not the case where a player is
integrated into an all-in-one, where they may be in a cavernous enclosure
with a nice hot amplifier in the bottom creating circulating air currents
to
carry the dust around that it drags in through the scores of air vent
slots
in the base and back. The situation is, of course, further exacerbated by
the inclusion of fans ...

You've pretty much confirmed my prejudices. "Everyone" is right, just in
different contexts. Thanks.