If you also remember to oil your rotary cutter when your rotary cutter is getting clogged with lint, it will stay sharper longer. I take mine apart often and oil the blade and plastic as soon as see lint built-up around the blade. Just a light film of oil does it, you don't want it to be sloppy with oil.
I hesitate to change my blades because they are so expensive to buy. Nowadays you can sharpen them yourself or you can go to Harbor Freight Tools and buy blades to fit the 45mm rotary cutter for set of blades for just $2.00. So at $1 apiece I change my blades a lot more often.