It seems like a lot of people have problems with rotary blades. So far, I'm lucky - I've not had problems. Yes, they do get old and not as sharp, but not in an unreasonable time. I do use a Martelli mat, and love it for its own merits. Not sure if that makes any difference, though. I also have their cutter, but don't use it as it's a very unnatural position for me. Hopefully, I won't ever get to the point where I need to use that style.
I buy my Olfa blades in a multi-pack when they are on sale. The larger packs are a bigger investment, but much more economical per blade.