How long were those studies going on for? I can do 12-14 hour days for a week, I even once programmed quite challenging code for 36 hours without making anymore

How long were those studies going on for? I can do 12-14 hour days for a week, I even once programmed quite challenging code for 36 hours without making anymore mistakes towards the end, but after I do this I'll be very tired for a few days once the rush is over.