Viewing a blade on its own merits may give you subjective results. Are you asking about metal or rubber squeegees? You really need to examine the print quality before you decide if a blade is worth using. If you are getting the right paste deposit volumes, then the blade is doing its job. Example - I have a metal blade that has a definite kink near the end. I don't use this blade to print large width boards because there is a definite solder skip caused in the paste. But it works fine for narrow boards where the paste print is happening in the center of the blade and not out at the ends.
Setting the right squeegee pressure and having a good angle to promote paste roll is most important. With these parameters maximized, a "marginal" blade can give good results. Condition of stencil, flatness of fabs and proper underside support are also paramount to getting good print quality. The squeegee, if well maintained could last years, where as the stencil can get worn out fast if all other parameters are abused.
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