You would want to go to idle when things get lumpy enough that a collapse seems inevitable...
Just for some perspective, I only ever remember one time that I did this, I was trying to break through an inversion on a very thermic day and drew the line at having to bury both breaks to stop a frontal... Above the inversion is likely to have been nice and smooth but I gave in, it beat me
If you get a collapse and maintain power, you are just asking for an off centre thrust line or oscillating thrust line to confuse the hell out of you just when you need your wits at 100%.