I could go 4 days or so in my 20's. my longest single shift of work (actual physical work, not inluding the longer shifts I worked where I took a security job for a couple months) is 36 hours.
when I worked the ship yards I worked 11 weeks of at least 12 hours a day and 2-4 18 hour days per week. no more than 4 hours a night of sleep during that and usually somewhere between 0-3.
about the time I turned 35 I just couldn't do it anymore. in my 20's I could go to sleep at midnight, wake up at 2:30, then drive 4 1/2 hours, pass an x-ray welding test then work 12 hours. no way I could do that now.