I work at CVS, and I get 40 hours a week when I'm not away at college.
How much you work depends on your store, how many techs you have employed, what kind of volume the store deals with, and the person in charge of scheduling. I'm lucky enough to have a store that does 700+ scripts per day, a good scheduling person, and sufficient techs. Therefore, I can pretty much decide how many hours per week I want to work.
While I'm away at college, I work once every 6 weeks to stay on payroll. We have people that only work on certain weeks, and other people work less than 15 hours per week. So, everything just depends on circumstances. If you look for a job in a pharmacy, just talk to them and explain your situation along with what you're looking for. In my experience people are understanding.
However, if you're looking for a tech position, CVS might be harder to get into now. I'm in South Carolina, and CVS is evidently now requiring that for ever 3 techs working, 2 have to be state certified (different than state registered). Which means you have to have worked so many hours, passed your PTCB exam, and taken what is evidently a year's worth of classes in order to be state certified. So right now, the CVS's in my area are only hiring state certified people.
Hope that helps!