It all depends on what you use for your cone and how much of it you use...my ducttape ones I use about 8 inches of skewer. there are no real advantages or disadvantages (that I know of) to length other then that the skewer needs to be long enough to be heavy enough to stay balanced which will result true flight rather then be cone heavy as with you wire nut darts
hope this helps, best of luck
hope this helps, best of luck