First signal the party is nearly over for long time shareholders. My personal sell indicator is when I can go into my local Target or Walmart and Wii will be in stock. Hope it doesn't happen soon as Nintendo has been very good to me.
Here is a dated but interesting web page. Using your logic, is it good that it it out of date? If it gets updated you may never buy back in. http://www.wikinvest.com/stock/Nintendo_(NTDOY)