The leaves in our front yard are not at the optimal point for raking yet. There could still be more that could be captured with one pass of the rake. Too many and you have to rake more than once, too few, you waste rake strokes.
But. Today is a nice day and it wouldn't be bad to be outside. Who knows what the weather will be like later? Do I want to rake in the cold and/or the rain to get my leaves to the curb before the last leaf pickup?
These are the constraints I face. Good thing I did well in my operations analysis and management science classes in grad school. There is undoubtedly a formula for this somewhere.
In the end, we are all dead. So it doesn't really matter.