I am not referring to the changes in CPU consumption such as you see with new features, changes to models, or greater/lesser efficiencies in the code. That is as expected.
Recommendations on max CPU usage when I first got my FM9, several firmware versions ago, were for about 80% or even a few percentage points above. Now I seem to be seeing recommendations for max CPU usage trending lower than that. Sometimes down to 70%.
Maybe it is only anecdotal, but it appears as if there are a greater number of issues being reported than previously with presets that are under 80%. Wondering if some of the "behind the scenes" processes that don't show up in that CPU usage number have gotten hungrier. Or maybe, those reports of lockups or output drops could be better explained by issues other than CPU consumption. No clue. Just echoing my maybe erroneous sense that recent firmware has resulted in recommendations towards a more conservative use of CPU when designing presets.
Any process that could potentially impact proper and full operation, would optimally be included in the CPU usage number. No unreported hidden processes that impact usage. That way you know exactly how high the indicated CPU number can be in your preset. Either that or it would be useful to know that there will be either a fixed or max CPU usage number for "system" overhead. Either of those would better enable you to calculate max CPU usage.