Selling and taking profit during the bull run is not ideal because after selling, you might not be able to buy back at the price that you bought before and this will make you have less bitcoin that the initial amount that you had before selling. Meaning that you don't have a bitcoin target and you are not focus on accumulating bitcoin on a long term investment. Another reason why this strategy is not the best is that you will miss out the compounding interest that your bitcoin investment will accumulate for you if you only keep on accumulating till 10yrs time or more. Try and see your bitcoin investment as your life savings and not for profit alone because nobody knows if at the long run it is your bitcoin investment will be the one to take your to the next level in future because there is high possibility that bitcoin price might keep on increasing with timeline. It is better to save for the future than saving to sell and take profit and buy back again. All bitcoin sold can not be bought back easily because of the change in price towards the upside. It is also a bad idea to sell all your bitcoin investment and hold fiat. What is things didn't work out as you planned it after selling, that is when you will regret your action.
I don't agree to your assertion that it's not ideal to take off profits within the bull run like what's the essence of investing? Isn't it to make profits? So in a situation whereby an investor have achieved his major aim of investing which is to make profits so after selling off his bitcoins the next for him to do is to pause investing for sometime until the price begins to dip then he can start buying and holdling again till he aquires a reasonable amount or better still he apply the DCA till the price skyrockets again so that's what an experienced investor does.
In trading, making profits is not guaranteed all the time so accumulating for a very long period like 10 years as you stated may not really be an obtainable idea as the future is unpredictable no one knows how the fate of the coin might turn out due to some uncertainty that surrounds the stock market. Making accumulation for a very long period of time might even lead to losses because in the quest of hoping that the price will skyrocket then it suddenly starts dipping so it's really not ideal to accumulate for too long as no one can speculate or predict what it's future holds.