I buy the 45mm carpet cutting blades at Harbor Freight. They run about $1.99 each. Some have not had good luck with these, but I haven't had any problems with them.
One board member posted that she uses a Sharpie to mark her blade with a dot, then if it starts skipping, she turns the blade over and marks that side with two dots.
I got one of the blue Dritz sharpeners, which doesn't really sharpen, but it does smooth out the nicks which cause the blade to skip. It's a temporary fix, but it does extend the life of the blade a little.
I have one rotary cutter which is a dedicated paper cutter for trimming printed patterns (PP, applique). When I change blades on my fabric cutter, I put that one in my paper cutter.
To dispose of the used blades, I have an Altoids tin that is clearly marked USED BLADES. I think I have a dozen or more in that tin and there's room for many, many more.