The suggestion you made not only applies to BTC but in investing in general. If you save capital in a monthly/yearly basis, the returns would be profitable in the following years given that it is unrecognized income. Though I agree with your suggestion, it must be considered in case-to-case basis given that the value of BTC is very inflationary and volatile.

In adherence to my above-mentioned statement, you should always convert your BTC into cash or to your desired currency if it reaches an amount higher than your initial investment. One thing that I learned over the years is that the price of BTC fluctuates and when you get too greedy, you might missed on the opportunity of converting your BTCs at its ATH to your desired currency.