Labs are up about 4 hours a piece for each report per week, plus lab time, when I was taking them. They weren't hard so much as tedious- you have to be thorough in your reports if you expect As. The classes themselves weren't so bad, but the homework could also be time consuming. We had Mastering Physics in my physics class, for instance, which could take me 2-5 hours per week. Keep in mind I'm a bit slower with math, and that I was doing A level work (aside from one A-) in my lab courses, so I might have overkilled it a bit. In summary, be prepared for some tedious work, but nothing excessively challenging.