Basically Bitcoin needs plan. And in my point of view anyone has Bitcoin or he is buying with DCA method so I think he should never sell all the Bitcoins at once. He always hold some amount of Bitcoins. And if anyone will believe on Bitcoin and will Hold for 4-10 years or even more so definitely Bitcoin will give benifits of his/her believing.
It's wise counsel for anyone considering selling all of their bitcoin to hold off on doing so by keeping some. However consider this, someone might decide to sell all of their bitcoin at a high price at once and wait for a bear market to occur when the price of bitcoin drops, at which point they could buy some bitcoin to hodl until the next bull run starts.
All of us, however, have our own strategies for accumulating and selling our bitcoin holdings whenever it is appropriate for us. It's not a guarantee that hodling bitcoin for years will prevent its price from falling to a point where it's affordable to purchase during a bear market.