First, it seems that scale is both an economic and a philosophical question. Perhaps one of the answers is to match economic need with philosophy. While I need more sheep to pay myself a living wage, I don't want to have so many sheep that I can't do most of the work myself, which suggests that there is some sort of "sweet spot" in terms of scale. My management skills have improved to the point where I can manage 200 ewes in the same amount of time it used to take me to manage 50. Following this logic, with the right management systems and skills, I should be able to increase our scale to 400-500 ewes without having to hire outside help.
Second, I have been reminded during this lambing season that even with 130 bred ewes, I recognize many of the individual sheep in our flock - I remember their past lambings and their behaviors. To me, this is part of being an observant shepherd. I'm somewhat surprised that I continue to recognize these individuals even as we grow in size. Perhaps proper scale is that size that provides sufficient income while allowing me to still pay close attention to individual animals.