An investor should have a goal. For example, how many Bitcoins he wants to deposit in his portfolio, for how long he will hold it. That does not mean that a person should always monitor the market. An investor can buy whenever he wants, but he has to be consistent. Waiting to buy is never right. You do not need to study the market to buy Bitcoin. If you have discretionary income, faith in Bitcoin and basic knowledge about Bitcoin, then you can invest.
An investor will never study the market before investing, he will always continue to buy consistently. A trader always studies the market. Our investment goal should be long-term.
Selling your holding before the expiry date will not be the right decision. If your expiry date is over, you can withdraw some amount of money and enjoy the profit, but withdrawing the entire amount of money just because your investment has expired will never be the right approach.
Well, how would you know that it is the expiry date and you need to sell ? I think you are referring to the time to buy or sell at the best optimal time, but again, it is impossible to time the market. You can consider today's example a case study where Bitcoin reached an all-time high, and Ethereum looked strong at over $ 4,700. The market sentiment suggested it would also hit a new all-time high.
Then all of a sudden the data for PPI came, which was not as expected, and Bitcoin dumped to 117500$, and Ethereum also dumped to below 4500$. No one in the world could have predicted these moves. That is why it is important to DCA while investing and also it is essential to take profits while the market is in a green and positive state.