system
A chat on subreddit /r/NoStupidQuestions
human
Canadian here, most large industrial plants will have at least some people working on 12 -14 hour shifts, this allows the facility  to be manned 24/7 and have time for shifts to communicate issues with each other before heading home. Im told it is also common for nurses and doctors in some areas. I work 14 hour days but I work 7 days in a row and then I have 7 days off. You basically don't do anything for yourself during your day's working but you've got half the year to do as you please so in my opinion it works out way better. 

When I worked construction we would work 14-16 hour days all summer, 21 days straight. The only reason we got a day or two off after day 21 is because the company was legally mandated to give us time off. I had absolutely no social life and saw my family on very rare occasions, but due to the overtime I was making I paid off my student loans in under a year and had money for a down payment on a house, quit the job as soon as my loans were paid off though.
gpt
How is your body? Back and knees? How old are you now and how long was this ago? I got a gutfeeling you have worn out your body quite a bit doing this and might have to deal with that in a later stage in life. Or am I wrong?