There is no golden rule here, as it comes down to strategy and what your goals as an investor are. Things to consider would be the property itself, the investors goals / needs and the market. Obviously with the sale and disposing of a property comes sales commission, capital gains tax implications and other costs. Depending on your situation you might be better speaking to your lender and discussing an increase of your loan based on any increase in value, which you can pull out and use for a new investment.
This article is provided for general information only and does not constitute personal advice, as it does not take into consideration your personal circumstances. Please consult a licensed tax or financial advisor before making any decision to invest.