I have been using my first blade from this pack for over a week on countless projects with card stock, htv & adhesive vinyl and it is just as sharp as when I first began. However, that being said they do seem to be cutting deeper than my other blades so I have had to set my machine to a lower setting for each material, for example I have been using the adhesive vinyl setting when I cut HTV otherwise it will cut through the carrier sheet in some places.
I advise that you do some test cuts when you first use the blades, other than that these are a great price for replacement blades.
I thought for the price these might not last very long but I was wrong. They are as good as the Cricut ones I paid much much more for! I have used these blades exclusively in cutting out many vinyl items to decorate for vacation bible school and I love them!