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.