the thing that bothers me is that there isnt a "safe temp" thus you have to get them hot to begin with to even see where it may be damaged. and it will not be the same between copper, aluminum, and china & american coils. not to variances in immensity and the sensor averages the temp within its view.
i happen to know the american temp at which coils degrade. you can also take them wayyyy higher then anyone has said was "good" then they go. just a note. if you have 150 to blow instead of learning your system, by all means, get it done.