How many hours do you attend school in a week? And how many hours do you work a day and throughout a week?
I took it pretty easy in the last two years. I kept the partying down for one. I would say 20 hours a week work, 25 hours a week for school (which includes class, commute, library research, homework). It basically came out to what amounted to a 40 hour a week job, but more interesting since part was work and part was school.
In semester units, that's 12 for fall, 12 for spring, 6 for summer, and repeat and rinse for a grand total of four years for about 120 undergraduate units and a degree. Realistically, most college students I know took two classes for the summer, every summer, and maybe an intensive holiday season intensive class or two during college instead of going 15 and 15 and sitting out three months only for work in the summers. One can tend to get rusty that way, imho.
In the first two years, you can work a lot or a little and it won't make a huge difference in your life, in that much of the first two years will be like a rehash of high school, just a bit harder. Some can handle a big schedule of work with school and others just prefer to do school.
It's final two years of college which count most whether you go to work or to graduate school. For work, if it's related to your bachelor's degree, your major will be heavily weighted in your junior and senior years of college.
If you attend graduate school, what most admissions people will be most concerned with when it comes to grades is how you did in your last two years and not just overall GPA. The applicant who got As and Bs in the first two years but finished with Bs and Cs in the second two years won't look as good as the applicant who had the same GPA, but finished stronger than they started.
And then there is the person who is a college student, and while there, they find more than just work but a career which takes them to big places to the point where school is secondary (sports heroes, rock stars, many high tech millionaires, actors, many big time journalists and commentators, and others). So keep an open mind and go to school with the goal of finishing college but don't pass on a great work opportunity if that comes up.
What units you have finished will still be there, but in the majority of cases, most of us are normal and should just finish college, once we start it, and find a normal job. If you are extraordinary, like Kobe Bryant, some A-list actor, or a genius of some sort, you are likely to hit some great opportunity. Those people who somehow become unusually successful young are ones you may see once or twice among your high school or college classmates and they are one in a thousand.
Don't work more than you need to so you can brag you finished college and worked more hours than anybody else. Beyond your first year after your degree, nobody will care that you finished college and worked so much you were a machine who never slept much in four years. That's about as smart as saying you finished college and drank more beers and smoked more pot than anybody you know. Life's too short to abuse yourself when you are in your relatively carefree years of your life.
Graduate school, or marriage, or career, or having kids, or worrying about home repairs, and the really hard work of life which isn't just a four year commitment, which can tend to suck the youth out of a person, will come soon enough to many people.
I say, work as little as possible and try and enjoy your college years as those and your years before that will most likely be your fondest. It's a cliche but one that almost everyone I met tend to share after one finishes their 20s, 30s, 40s, and beyond. Life gets harder with each year, physically, after age 30, but what you get in return is experience and wisdom. Some days I am happy to have gone through secondary school and college, but other days I wish I was still there.