My right rear regulator failed last spring -- first one in 12-yr old vehicle. My theory is just the opposite: if they're used regularly, better chance the cable/pulleys don't get "stoved-up." The left rear one on my M3 was the first (and only, knock on wood) to break -- so same reasoning: those are the least-used regulators. In both cases, it was the cable wheels/guides made of PLASTIC that got brittle and broke, so it's a losing battle when they're built to fail.

I agree.
In the last week I've been traveling where it's over 100 degrees everyday,
and one day was a 115-
as soon as I jump in ,
all four windows go straight down to let some heat escape,
I never give a thought to regulators breaking!
:whew::

I don't even bother to get in... ;) I just remotely open all the windows and crack the pano roof with the unlock button on the key. We also very routinely hit 100+ in the summer. Actually, we only have 2 seasons here; summer, and January.