I bought a pack of 50 for £20 on ebay, all the same size but it is generally the size i use most of and have been doing a lot of work that needed them with customers jobs, my own rentals and also my own house renovation and i am about half way through the pack now after buying them in November. It is like anything, if you abuse it and try making it work too hard it will fail, but just go steady and let the blade do the work and they last much longer.
