I just wait till JoAnns has one of their super sales and get a couple extra blades really cheap...like 4 bucks
I replace mine anytime I think it is getting dull...sometimes I feel like I can mess with it being dull and if I am doing alot of cutting I put in a new sharp blade.
I do use my old blade on photos I have printed and some card and scrapbooking stuff...then throw it away.
I also keep the little plastic thing it came in to use to dispose of it so no danger of anyone getting cut from it.
Kirsten