Sounds like your bobbin winder works. Mine wasn't adjusted correctly and could never get it right. A 'good' bobbin only wound about 3/4 of the way. If i tried to get a full wind, it wouldn't stop and I would get about 10-15 yards of thread wrapped around the post. Finally got a stand alone winder.
http://fancyquilt.com/store/viewitem.php?productid=0
Love it!
As far as how many bobbins to wind, I agree with the poster who said you will learn with experience. It really depends on how much quilting you do on the quilt. I've used 1 bobbin on a crib size and used 3 on other cribs.