I have always wanted to make one of those big chunky blankets.  And I knew just the birthday girl who might like it.  So, I purchased 2 big balls from Woolly & Co.  I could have used only 1 ball and still had a nice size blanket.   However, I ended up using part of the second ball to get the length I wanted.  It is the quickest knit with such pleasing results.  It literally took an hour and a half!
I cast on 23 stitches onto my arm. :)  And knit until the piece measured about 70 inches
Finished Measurements ::  42" x 70"
(If I were to use 1 ball, I would cast on 18-20 stitches and knit until the ball runs out!)