Back during the Loadmaster days, we had to go longer than the flight crew due to load, monitor and then unload.
I think a bit over 48 was the longest I ever had to not only stay awake, but also stay sharp..
They had some good meds for us that helped but damn it caused a massive crash when you stopped taking it..
Since then, I've gone a bit over 24 hours until I said
"To hell with this" and passed out asleep no matter where..