I think it depends. If you are doing it for a certain period of time with a tangible goal, then it might make sense. For example, if you know you can pay off your student loan by doing overtime for 6 months, then that might be a good idea even if you don't like working that long hours, because it is a tangible goal with an end in sight. If you are just doing it to get to ER faster but doing it for an indefinite time, then no, it doesn't seem to be worth it since it would most likely make you miserable.