Here is an article we (Peter) wrote on the topic for Canadian MoneySaver.
Generally, we want to let winners run, until 'something changes', be it management, debt, execution or continued mis-steps. No one goes broke taking a profit, but no one gets 10,000% returns if they sell after a double, either. We like to trim for portfolio management reasons: we do not want to 'bet' on a single company. When considering a sell, we like to put ourselves in the buyers' shoes: Why are they buying? They are not buying the stock with the expectation to lose money. With core, reliable stocks such as those mentioned, we would prefer not to trim. But investors need to be prepared for corrections, and if investor timeframe is short, or one is prone to 'reacting' to sharp market movements, then trimming is certainly more of a viable option.
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