Mine gave up for reasons completely unknown.  It was never stored outside of
its protective case.  About half way through the dive, I noticed it was
leaking badly.  After the dive, I looked it over and found one of the
uprights was broken.  Several others have reported similar experiences.  In
my personal opinion, the mask is a piece of overpriced junk, but like I
said, I know at least one person who has had luck with his.  I hope you have
as much luck with yours.

At first, the dive shop claimed it was my problem.  I was pretty clear with
them that nothing I had done had caused the problem.  The shop agreed to
send it back to Mares "to see if they would cover it."  A couple months
later, I still had no answer.  I happened to be in the ship while the Mares
reps were there.  I took advantage of the luck and discussed it directly
with them.  The agreed to replace it with another one just like it.  I
negotiated a change to a new, higher view two lens mask they had as a
sample.  It was a nice mask and fit me well, but was not available yet.
Several months later, when it became available, I found that the final model
didn't fit.  So, I paid well over $100 for a mask that broke and traded it
for a $50 mask that doesn't fit.  I suppose you might say that the warranty
covered it, but you might also say that I got nothing useful from the
warranty.  I'm back to using my previous backup, a Tusa Liberator.

The Mares was supposed to be a replacement for my USD three window mask.  It
lasted 15 years before I managed to break the plastic frame.  That one was
my fault and, even if it had not been, I would have been pleased at its
service.  Unfortunately, the mask was out of production.  I could not get an
exact replacement, hence my giving the similar Mares mask a try.

Lee