For a long time, I used stands for my brushes, with the knot facing downwards. Then, during a conversation with a custom brush seller, he mentioned that storing the brush upside-down in a holder actually kept moisture at the knot base for an extended period of time. Since then, I have always stored my brushes on their handles, lofts up, with no problems at all. That said, a thorough shaking off of the brush after use, followed by brushing the tips on a towel prior to storing away on an open shelf, as mentioned, is necessary in this case.