I have had a couple of M42 blades snap on my Felder bandsaw (Italian, so not made by Felder, but still a quality machine). I am an amateur so the machine isn't used every day or even every week and the blades certainly did not last 5x the life of a carbon blade. I discussed this with Ian and we concluded that it might be to do with the fact that the machine sits idle for quite lengthy periods and machines will often come to a halt in the same position, meaning that the same parts of the blade will be bent around a wheel when the machine is not in use. He hadn't heard of the problem from users but that may be because less frequent users like me are less likely to buy these blades - I buy them because I hate the faff of blade changing.
Ian suggested releasing the tension after I finish using the machine - something bandsaw makers often suggest but I doubt that many users actually do it. I now do this and have a sign on the machine to remind me; so far so good.
Jim