1. It sets the stage for your career. Do you want to spend the rest of your life working evenings and weekends? No? Me neither. That's why I decided to only work relatively normal hours. I'm practicing for the future. I find that having limited time to work makes that time more productive (see point 3). I've also accepted that I might have been able to do more work if I had stayed longer hours. But, I'm okay with prioritizing my happiness over a potentially prestigious future job that would stress me out. By setting the amount of work time I have each week, I contain myself at a level that is sustainable in the long term and isn't a stress-work roller coaster.
2. It makes you visible to the faculty. The majority of faculty members work during normal business hours. They aren't constrained to, at least not by the university. Mostly it is because this schedule fits best with other factors such as when other faculty members are around, when kids are in school, and when classes need to be taught. Regardless, the best time for you to be in your office is when they are around to see you. Yes, graduate school is not about working hours, but about accomplishing certain tasks. However, professors are still human. They are more likely to believe that you are making progress if they see you in your office everyday than if you work evenings when no one is around.
3. It increases productivity. I've known graduate students who spend long hours in the lab and at their office. You may be one of them. They always have so much to do and not enough time to do it. They also tend to be the ones who take long coffee or gossip breaks during the day. Now think about what would happen if they took those breaks and worked through them. Instead of having to pace yourself to survive a long work day, you could plow through it, knowing you get to go home at 5. Plus, there's also the motivation of a time crunch. If you only have limited hours to work, you have to make them count.
There are, of course, some caveats. Field work is exempt, for obvious reasons. If you are still taking classes, homework may pose an issue. I chose to try to complete homework at home, in my off time, leaving my 9 to 5 day for research. You can also choose to make homework a part of your work day and leave any large projects or hard problem sets for after hours. The same goes for teaching assistants. Decide if you want to fit grading papers into your daily schedule, or if you are prioritizing that time for research.
Then there are the important research activities. The paper that is due tomorrow, studying for exams, practicing a presentation. There is no need to restrict these to your 9 to 5 day. You can stay a little late, take some work home over the weekend, whatever it takes. As long as it doesn't become staying late everyday and working every weekend.
Lab work is another problem to the 9 to 5 work day. If you can do your labwork within that day, great! If not, consider trading hours between your work time and home time. For every hour you stay over to work in the lab, take another hour off on some other day. Do you work late two nights a week? Then leave on Fridays at noon. If at all possible, try to stay true to suggestion #2 and schedule your lab time to overlap either normal working hours, or when a faculty member will be around to see you working.
Overall, working a typical 9 to 5 shift as a graduate student can be beneficial for you. Be careful not to take these recommendations too strictly though - they can be easily modified and still achieve the same effect. For example, I work best in the mornings, so my "shift" is closer to 8 to 4. I also do better with a long, non-work related lunch break. So I make up for this time by occasionally taking home books or papers to read. Figure out what works best for you and stick with it!
So, how do you normally work? Is a 9 to 5 workday reasonable for you?
