If you have ever looked into a hotwire AFM, They have very fine wire which wouldn't take too much to damage - saying that 100,000kms on a car would have to take its toll.
Usually there are 2 - 3 wires, which measure resistance (hotter = less air flow, cooler = more air flow) which can be measured via voltage - hgow much current will flow through it. Basically they are unrepairable.
Cheers
Sumo