As a lab assistant, how many hours per week am I expected to be helping out? I am in my third year of computer engineering studies, and was offered a position as lab assistant in the electronics lab. I am oriented towards software, so I'm not exactly interested in the subject itself, but to my understanding, being a lab assistant is quite a good thing for the CV, plus it's good to be a familiar face to a professor or two, and I like the work, so I'd generally like to continue.

What makes me skeptical is the fact that I am in the lab for two hours on Monday evening (I miss the first hour due to an overlapping class), three hours on Thursday evening, and six hours on Friday from 3pm up to 9 o'clock, which brings the total time up to 14 hours. While I can probably cope with that, I was also asked to grade some reports (is it even legal for undergrads to grade undergrads?), a subject I want to discuss on another question.

At any rate, I have felt a big impact on my independent pursuits since I started, namely some days I'm at the campus all day so I don't feel like I'm doing much, and I really can't stand not doing stuff.

The question comes down to this: As an undergrad lab assistant, how much time am I expected to devote to the lab, and how much work am I expected to do at home? How serious a commitment did I make?
In graduate school, this would be dictated by your GRA (graduate research assistant) contract, which would specify a minimum number of hours you would be expected to work on research each week.

As an undergraduate research assistant, if you're getting paid OR if you're receiving credit for your work, I would expect this to be dictated by your contract or a syllabus (respectively). If neither of those conditions are true, then this is a matter to take up with the professor you work for. Consider telling them that you would like to cut back on your responsibilities to pursue other interests, but know that they might counter with telling you that you're no longer needed. Negotiate carefully and respectfully.

For the record, 14 hours doesn't seem too extreme, even for an undergraduate research assistant. And if you're being paid, whether or not you can be asked to grade depends largely on the terms of your contract, though it doesn't seem unreasonable. In any event: negotiate respectfully with your boss, just as you would do in any other job.