depends on the person who do it.How experienced he is.
If you know what you are doing you wil find it easy to go by sound,smoke and performance.
The only time i use the tempgunn is to verify that the temp is stable.

Here in norway the airtemp goes from 41 to 86 in the summer.
So we can not tell somebody to always have 240 on the plugg.

outside temp and humidity and nitro prosentage and engine are all making a difference.
So in both way u can ruin your engine.