I'm ranked in the top 25% or so of my class and am taking 21+ credit hours every semester here with an engineering major and a minor. I spend about four to six hours a night on work, though I try to space it out throughout the day. It's a lot. I don't put nearly as much effort in as some of my peers with school. I procrastinate and rely too much on being naturally mildly good at academics to get through my classes, and it works for me, but do as I say not as I do on that one.
I'm involved in upwards of eight clubs so I spread myself a little thin. I could sleep more if I chose not to get involved in such things, but I value experiences a lot here. If I took an easy major, stayed uninvolved, etc, I could sleep eight hours a night every night. That's boring though.