A workout is only as good as the adaptations it produces.
The idea behind lifting weights is to force your body to adapt to new stimuli by creating greater strength through muscle growth. Older and more experienced lifters are going to adapt to a workout faster than younger or less experienced lifters, because our bodies become adept at adapting to new stresses the more we expose it to them.
There really is not much to disagree with on this rule. Basically, you want to get the maximum adaptation in as short a time as you can, and then move on to new workouts.