yes, reliable. Yes, they can fail completely.
I guess the point I was really trying to make was that they are in a state of decline from the moment of manufacture (the heated wire), obviously it's a time not use thing. So, eventually they might not fail completely but they can be in such a poor state that they are worse than not having one (the value it's sending is so wrong, so out of relationship with the air flow, the device is useless).
Sorry I was referring to the EGT sensor in that post, not the MAF.
Solution for the MAF issue is replace with a MAP sensor and Link ECU / 2ZZ