I had always understood that the "generally accepted" period where a sale becomes 99% safe was at 6 months, although there can always be exceptional circumstances and I have seen around 8 months in the gambling industry a few years ago.
It would be good if there was a fixed time limit but if you stop thinking like a site owner for a minute, and think like a customer then if you really didn't spend that money but were too busy, too rich or too stupid to notice, then why should you not get the chance to get it back, regardless of when you noticed?
Anyway people, just to be on the safe side, better not spend any of today's sale proceeds until middle of April 2010.
