Not sure if it helps, but I know with my Pandora account ages ago I bought the "Pandora One" membership (was a one time fee for life, gives more skips, HQ streams, no commercials etc)
I use it about 8 hours a day, no skips. Am running CM7 if that helps?
Last night by mistake I left it on when I went to bed. ~11pm till 6am and that sucker used 350 meg in bandwidth. :X