I'm not the person to respond to this post, but I'm going to anyway:>) I use my blades until they are almosted rounded instead of razor sharp. Then I store them in the pastic container they come in - in case the day comes when I'm out of new ones and really, really need a different blade. The old stored blades are used for cutting chores around the house; paper, cardboard, opening packages, etc.
I keep promising myself to order some from Harbor Freight, but I never seem to get around to it.