I have two bullet cameras that are 2-3 years old and where the built-in IR has stopped working, (even after cleaning). Entire ring of LED's is out. Cheap-assed cameras, but still work fine except for that. Seemed a litte weird at first, but something's got to go first on any box, right?
Put another way, when you have to return/repair/replace a camera with built-in IR, how often is non-functioning IR the reason?
btw, I was pretty sure there was an IPVM article or survey on "Why do cameras fail ", (in the hardware sense.) but I can't locate it. If not, maybe it would be a good added integrator survery question in the future?