http://www.gearslutz.com/board/showthread.php3?t=9790
Discussion starts at post #10. Wes suggests vertical storage of long-ribbon mics to prevent long-term stretching of the ribbon. He has way more experience with ribbons than I'll probably ever have. That said, I just picked up a pair of 44A's that have been sitting in a box (not vertical) for the past 50 years or so, and they sound just fine. Could they sound better had they been stored vertically? I don't know. But I don't have any desire to get these re-ribboned.