I use Olfas and they seem to last me a long long time and through several projects. Like quiltstingz says polyester batting and some flannels tend to dull the blades faster. I have found that some of the white plastic mats also damage the blades. For me, a long time is 5 months not 5 years..... I use 60mm for more than 4 layers and 45mm for the other and I buy 45mm in 5pak. They are a little costly but that way I know I have a spare when it's needed, especially when at a quilt retreat!!