Welcome to the fold!  ouch.  The actual amount of data transferred between Stanford and you and back is very little.  If by 6.0 you mean 6 mbps dsl, then you're faster than I, and I don't notice any effect on my connection.  As far as leaving your pc on all the time, I do without problems.  I have mine on all the time for two reasons:  I'm an old dinosaur that still believes that the stress and thermal cycling of turn-on turn-off operation is worse than the wear from continuous running; and, obviously, the more it's on the more work it can do.  I did some calculations a while back and figured it cost me $11/month extra to keep her on all the time.  I think you'll find that folding is a "good thing to do" that has little or no downside for you.