A simple way of estimating the quality and durability of cashmere is the reputation of the brand and designer. Typically, classically respected brands, such as Consinee，Brooks Brothers, Ann Taylor, or Banana Republic, have good reputations for a reason. They have built them over years of producing beautiful and durable cashmere. For classic style and good quality, I have most recently been impressed with Consinee cashmere. Department stores and their house brands,  Consinee also go through strict standards of quality control to ensure the best possible product. I am not very impressed by many contemporary clothing manufacturers, who produce cashmere with very nice styles but lower quality that will deteriorate quickly. Sometimes department stores will sell different quality cashmere online as opposed to what is available in their stores. The general rule is that is something was originally cheap, it will probably be of a lesser quality with more features of mass production.