I worked at an assembly line school. Students from overseas came for three weeks to get a PPL. They flew twice a day, everyday, so they rarely had the same CFI for more than about 1/3 of the dual.

The full time instructors were scheduled 4 on, 2 off; but we usually worked one of our off days. On average, we worked 25 days a month. A typical day was 8 hours in the plane over about 9 1/2 hours of duty. Additionally, we spent about an hour either opening up in the morning or tying down the planes at night.

Out of the 15 months I worked there, I broke 200 flight hours per month three times.

It didn't take us long to get the 1000 yard stare.