Quite by accident, I bought very large blades for my rotary cutter. It seems like they are lasting much longer then the size that is intended for this rotary cutter. I have used this one blade for cutting 2 quilts, lots of pieces, and even some batting.
I was told by someone in quild that to cut batting with the same blade will really dull it. I got "lazy" AND JUST used the same blade, and it is still sharp.
Don't know that there is a scientific reason for this, but it is working for me!
Mariah.