I use about one blade for one quilt. Sometimes I can get many quilts from one blade, but not if it is a Bargello. I just finished a full sized Bargello and it took one blade. I can't help but think something is wrong if it is taking you that many blades. Are you cutting on a mat? I use an Olfa mat. Maybe that makes a difference. I wouldn't think that holding the rotary cutter wrong could make a difference...but maybe that is it? Could you be holding it wrong?
I am sure that someone here will have a better idea of what could help you, but something just doesn't sound right. I use Fiskars blades. Maybe that makes a difference? Or maybe you accidentally put in two blades at once. That would make them not cut right...
I have not heard of anyone being real excited about the blade sharpeners that are available, but I bet that there are those here who do know of places to buy larger amounts at a discount. I just buy mine at Walmart.
Warning about this hobby. It is addictive....(and not cheap). I have been a sewer for 50 years and started quilting 4 years ago. I just finished my 75th quilt. (like I said, addictive...)
Welcome to the hobby.
Dina