I don't disagree with you about it maybe being an overburden, but I still think it's a good learning experience. My sophmore year was a real shocker for me. The first semester I had my first upper level science class (ochem). Then, the second semester I had 4 of them, 3 of them (Ochem 2, Genetics, and Biochem) with lab. It would have been nice to gradually ramp of my course load but that wasn't an option. Considering that Bio 2 usually isn't harder than Bio 1, just different (at my school bio 1 was organismal biology and bio 2 was cells & genetics) OP should be able to handle Bio 2 easily in the summer session given his grade in Bio 1. However, Gen chem 2 is harder than gen chem 1, so it's really up to the OP if he/she thinks he can handle it. Although the classes are more condensed it's definitely easier to to focus on 1 or 2 classes, at least it was for me when I took two summers of classes. Sure, taking multiple prereqs in the summer might look like someone is trying to lighten their class load, but if they back it up with a semester or two full of hard classes, I think that negates any doubts.
With all that said, OP if you're a freshman and you've taken a full load each of your first semesters, there's no reason to rush through prereqs unless you're trying to double major or graduate early.
