Sure, you rinse your toothbrush after you use it and store it upright to dry. You may even soak it in 3% hydrogen peroxide or Listerine mouthwash to reduce the bacteria on it.
But you still need to replace it every three to four months — or more often if the brush frays. Why? It harbors bacteria.
Clean your toothbrush regularly and replace it at least four times a year, the American Dental Association recommends.