Making a certain amount of profit is always a good thing. Those who hold Bitcoin for a long period of time probably have other sources of income, as they keep their investment intact. This allows them to keep holding on to their Bitcoin.
An additional source of income is always essential when trying to survive in a speculative market. That income is your cushion from mental distress while giving you enough time to turn the tables and profit from crypto. That is why I always discourage anyone with the rambo idea of giving up jobs/properties or gold for bitcoin.
Because they are used to the ups and downs of the market, they have also learned how to trade without panicking. This means that selling some of their investment to make a profit at certain times would be a sensible move.
Some of the investment can be sold as per need. Some should be kept for emergency too. There is an existing problem of less exchanges available or big taxation from the government. At present, the avenues of selling is less in many countries.