I don't understand how people with 12-14 work days, make time for education given the potential lack of sleep. Let alone, not suffer from sort of mental deterioration. I guess when you are living in slave like conditions, you aren't thinking about that. I just don't know how they aren't suffering from some sort of psychosis?
There is a lot of research that lack of sleep (under 7 hours, likely 7-9) causes significant problems with memory, working memory, and is directly linked to cancer and Alzheimer's in later years.
In short, it might be feasible in the short term, especially if they have mindless jobs where they can study. I memorized a LOT of vocab during my factory work summers. But it has to be repetitive and mindless for that. I did more thinking at the factory than I did at software jobs.
Anyway, any time anyone says they work 12 hours and study, I don't believe them by default. Once you factor in commuting and maintenance, it's just not realistic...unless you are in a sweatshop dorm, I guess that would save on commuting/grooming/meal prep.
It absolutely is bad for you in the long term. However, given everything else, that might still be their option.
Ie: work 12-16 hours of labor to put food on the table, then study so then get a better job a few years down the road, vs work 12-16 hours a day for the rest of their life just to survive.
This is where UBI would help so people can work in their things besides basic survival.
I think it's a combination of youth and dedication that helps people push through such harsh circumstances. There was a time in my life when I would only sleep for 4 hours a day 2am to 6am and I did this for 2 years. Some good things were that I didn't work during the daytime, only studied, and I had access to very good nutrition. If I look back even I marvel at how this is even possible. But I was very young and super passionate back then. Definitely can't do it at this point in my life.
Definitely didn't take naps during the day since I was outside the house throughout the day. Weekends, I don't recall tbh. May be I cheated during the weekends. Not really sure.