I say 16-24 hrs during school, and full time or more during summer, which is what I did.
(1) It's a balancing act, try to be flexible about work within the limits to accommodate tests. Try to anticipate working well ahead of changing study work load.
(2) Be dependable and steady at work. Pharmacy is a small world. Nothing burns bridges faster than be known as a sh*ty unreliable intern.
(3) Good GPA isn't just a number. It's scholarship $$$, awards and honors that you can't buy, tax free, no effect of FAFSA. Working doesn't always pay more than studying more.
(4) Your post graduation plan. Residency? Keep a 3.5 GPA to be safe. Retail? Doesn't matter. Low GPA already, no chance for scholarship $? Might as well work.
(5) type of work. Hospital? You can often study on the job. Retail? No time to even take a piss. Guess which one is easier on your grades.
(6) Scheduling matters. I scheduled to working every weekend, then picked up a open shift when nothing is due. 16-24 hours/wk interfering with school at all.
(7) Summer = $$$. Work 40-60 hours during the summer and you can easily make as much in those 3 mo as in the whole school year. Learn to save rather than spending in on
H&B.