There is sufficient evidence in diving medicine studies to say that in
normal divers without ever experiencing mild DCS, that prolonged diving
over years change the airways of the lungs to lead to increased resistance
to breathing.  This leads to chronic bronchitis-like condition but there
isn't enough damage to require treatment.  Studies have been done on
healthy individuals who do not smoke.

What does the list think, particulary those with many dives under their belts?

In addition, there are other changes long term, as summarized in these
articles.  A full article is available from Medscape if the list requests it:

Medscape Orthopaedics & Sports Medicine

Long-term Effects of Diving

Ernest S. Campbell, MD, FACS, Orange Beach, Ala. AbstractAs the popularity
of SCUBA diving continues to grow, scientists are better able to determine
what the long-term effects, if any, are on the human body. For every overt
case of decompression sickness that is treated, there are many divers with
covertly-occurring intravascular bubbling, whose ramifications we are just
beginning to understand. We know that at least one-third of the population
has a patent foramen ovale, and those individuals who dive are at increased
risk for right-to-left shunting of air bubbles and the possibility of
arterial gas embolism. Another group at high risk for adverse effects is
professional divers making repeat deep dives with shortened decompression
times. The most well-known adverse injuries of diving are dysbaric
osteonecrosis, hearing loss, and permanent neurological deficits, usually
the result of a decompression accident; it is speculated, however, that
these effects may occur without decompression incident or injury. Reports
of cognitive dysfunction and damage to the liver, retina, and heart of the
diver with no history of decompression sickness are now emerging. Because
these symptoms may occur gradually and away from the dive site, prudent
physicians should be aware of the signs and symptoms related to adverse
events of diving in order to minimize the morbidity and mortality they can
cause. [Medscape Orthopaedics & Sports Medicine 2(5), 1998.  1998
Medscape, Inc.]

Warm regards,