My way is to monitor stock price gain in the last 90 days (once a month). Hold the top performers as long as they perform. Sell a few losers and under achievers every month and buy top performer (up to diversification limits). In a taxable account it gets expensive to sell stocks once they get to $100K in gains. Those are best to hold for the heirs. But they can be trimmed over a few years if they stop performing.
Much depends on what kind of stocks you buy. I prefer growth stocks that have reasonable PEs. I will usually hold them as long as they perform. Very high PE stocks and no earnings stocks to me are speculative. They have to be watched closely. Those are ones I might sell sooner–once you have a nice gain. Its always possible to sell some of a winner and reduce your risk.