indeed air traffic controllers are limited to one and…
Page 209 indeed air traffic controllers are limited to one and a half hour to two hour shifts before they must take a break, newer controllers can manage even less time because they haven't built up enough stamina controllers not only have to listen for information like pilots requests, and read backs of instructions. They also have to listen for any trace of unease or confusion, in pilots voices to assess when things could be getting. dicey in the cockpit.
— from Time