I just keep mine in the holder that comes in the box, but these numbered cases sound like quite a good way of remembering which reed to use if you're using them in rotation. I'm like Sue though, not organised enough, and like Tom, not obedient enough to do it properly, I tend to go by the markings on the stock of the reed as to which one I use, and my favourite one tends to stay in my Mr Lucky's 'Sax-o-glue' holder, formed from an especially absorbent piece of card.