But that itself is predicated on caring on having the stock whenever it does peak. If that doesn't matter to me, I can be happy with a relatively large profit, even if it isn't the absolute most I could have made later on.
To me, one criteria would be to sell when the company's stock price goes well in excess of record prices (or a price not hit in many, many years). Or just goes well above what seems reasonable (subjective, of course) for the time.