I have used both the Olfa and Fiskars (cheaper) 45" pinking blades. In general, I found them to blunt more quickly, However, I haven't used them before washing the fabric to reduce fraying. While I can resharpen my regular blades, I haven't found a way to resharpen the pinking rotary blades. I find it simpler to snip a small triangle off the corners of my fabric before washing in order to prevent fraying.

Try here for some ideas, hints, etc for using decorative blades for more than just 'pinking before washing'. :)
http://artfabrik.com/follow-these-ru...tive-blades-2/