I heard the Accuphase 100W Class A monoblocs (A-250s) in action a couple of weeks ago. They have the entertaining feature of an instantaneous digital readout of the power output, refreshed every second or so (it gets a bit hypnotizing). We played the entire Bernstein Mass VERY loud into a pair of (91dB) Fyne Audio F1-8s. For the most part the display showed an output <<5 Watts, rising to barely more than 30 Watts in the most dynamic peaks. I think the highest I saw was still <40 Watts.
What this suggests to me is that if you have a Class A amp which will deliver a solid 30 Watts in Class A, but reverts to Class AB for headroom above this, there are probably very few occasions when such an amp will depart from Class A into Class AB, unless you have inefficient loudspeakers or are trying to fill a large room to ear-bleeding levels.