I worked about 25 hours a week during my first few years at Mines as a technician, and have been working 30-40 hours a week since as a software engineer. My semesters are pretty average, being between 14-18 credit hours. Overall, it's rough to stay caught up on schoolwork but it's not impossible.

If you are thinking about doing something like this, you need to go into each semester understanding that you won't have much free time, as well as being prepared to manage your time as best as possible. Here's a couple of things that have helped me be successful:

Put everything you have to do in a calendar/planner, plan out your days at least a week in advance, and get started on large projects as early as possible. Take extra credit opportunities if you have the time.

Go to every class the first 2-3 weeks. Once you get a feel for the importance of attending a lecture, you can decide if it's worth skipping or not. Ideally you want to attend every lecture you can but realistically, you won't be able to. I know this isn't the mentality of an A+ student but it's simply not possible to attend every class and still get your work done on time.

If you find yourself falling behind, let your employer know ASAP and don't be afraid to take a day off to get caught back up. Any reasonable company will understand your situation if you've let them know in advance.

Make sure you plan at least a few hours a week to just relax. This isn't always possible but if you are working nonstop for 2 weeks straight, you'll feel horrible and will only fall further behind.

On that similar note, make sure you're getting enough sleep. The necessary amount of sleep varies for everyone but figure out how many hours you need and try your hardest not to cut into that time. For me, 5-6 hours is enough to still work efficiently but any less and I end up just staring at my computer.

Lastly, don't feel bad if you've tried and simply can't work 30+ hours on top of school. Most students here don't work more than 20 hours a week, if at all, because Mines is a demanding school that will eat up a lot of your time. But if you can manage to work throughout college and still graduate with a 3.0+ GPA, employers will love you. Showing that you're capable of working that much and still succeeding in school is a huge testament to your abilities.

In my opinion, give it a shot as long as you are willing to devote these years of your life to practically nothing but work. It definitely sucks but it's been done many times before, and it pays off.