I wouldn't bother reusing one, but I always keep a few spares on hand anyways, they're not worth the effort of removal (nor do I think they're worth reusing once you bang 'em out). You do need one to properly set the preload on the headset bearings, weight weenie or no, unless you use another method of doing so, like the compression plugs for a carbon steerer, or Azonic Headlock or similar...