I also buy in bulk Amazon. There doesn't appear to be much difference in life of blade and when new, they all seem to cut the same. There is just no way I can find anything good to say about Olfa Endurance Blades. My first blade truly lasted but everything since that first experience has been very dismal. I sent repeated emails to OLFA and even mailed back dull blades that didn't last. I never heard a word from OLFA. Nothing. Needless to say, I go out of my way not to purchase blades from this company.