Siegor: I don't think it's age as much as physical condition and/or congenital problems. An average adult in his 30s could probably do it without any major health problems. It's still a stupid thing to do even if you're 18.
I have my doubts - an average adult in his 30s might be able to stay up for 48 hours but 72 hours? My guess is most will involuntarily fall asleep before too much harm is done.
36 hours is the most I can be up before I fall sleep for at least 12 hours. And even after 36 hours without sleep I start seeing weird stuff such as blob-like phantasm squirrels coming in and out of tree trunks so I really don't want to know what it's like after 72 hours.
Back in 2010, I could stay up for longer. I once didn't sleep for two nights and on the third day I flew to Japan which is a 10 hour flight and I even managed to make a painting before going to my hostel and falling into a deep sleep. On the next day, I felt fresh and had no jet lag or anything but I was basically up for 3 days before that and traveling/painting is a bit more taxing than just gaming. Nowadays, I wouldn't be able to do something as extreme even if I tried.
edit: I didn't really sleep on the plane either so that was basically 3 nights without sleep.