If you don't like 40 hours of overtime on top of the base pay you already agreed to work for, then don't take it.
I for one have bills to pay, family to give gifts to, bank accounts to grow, investments to make, and might actually enjoy my job.
My only problem is I live with my gf who is unable to work (moved countries so in the process of becoming able to work). And while 80 hours a week on my 12 hour night shifts rakes me some good money, it's not fair to her or my family. I did that amount of work for half a year and fell out of contact with my family, and was miserable, I get the mentality of "gotta do what you gotta do" but hours like that are never worth it. I enjoy the shit put of my job; but after that "grind" I lost nearly a year of my life, just to be comfortable for that half a year, issue is working that much you can't enjoy it.
Which is perfectly acceptable and a valid reason for not doing that. But if that isn't your reaction or it doesn't bother you then you may be willing or even enjoy working those types of hours despite the negatives. Some people do this while they can in preparation for the future. Some want to do this to get into a position where they don't need to keep up that level of work but still maintain the level of income. Some want to retire early enough so they can do still enjoy doing the things they love. It really depends on the person. As long as your not someone who complains that they don't get the same "perks" as someone who did put in all that work and effort, it's all good.
I for one have bills to pay, family to give gifts to, bank accounts to grow, investments to make, and might actually enjoy my job.