During my entire 28 months as an active CFI, I rolled up an average of 56hrs per month over that time. That doesn't include any ground time, of course, of which there was a good amount as I was doing a lot of progress checks and such, not to mention the inconsistent weather... and I was also averaging 11hrs/mo over that time flying corporate for the same company.
Long Island flight school, not 141 but it was run like it was.
Just went back and looked, and my high month was 106.5 hours, though that included some personal flying. Only three more months were over 90hrs...