When I was getting my first research experience, I was working 5 hrs/wk in one lab, 5 hrs/wk in a second lab, and 6 hrs/wk at the arboretum. But all of that was to have a range of experiences to built up my CV for applying to a better undergraduate lab position. At a research university, it can be hard to get a good undergraduate research assistant position, because you lack experience. So, I did a variety of work the quarter leading up to when I wanted to start research in a lab that I would be willing to dedicate 10+ hours to each week. I had to do the grunt work and it wasn't necessarily what I want to research in graduate school, but I had a more competitive application for my current lab. That said, now that I'm in that main lab, I definitely agree that you need to dedicate more time to one than a little time to many. I do 10-20 hrs/wk in this lab now, and see a big difference in my relationships with my labmates and advisor.