Not sure what environment you are flying in, but I'm using mine offshore in the tropics (mostly). Estimate that in the last 5 years I have put about 2500 hrs on them. As I said failed 3 times. Once was a buzzing in one ear cup, the other two were failed cords (broken wires).
I too liked the noise cancellation, however when the batteries go dead there is zero protection.
Mostly I'm not impressed with Bose not standing behind something that is clearly a weakness (cords), this last mic assembly only lasted 2 years.