No one knows what will happen in the future, but during the current or next year it will be a golden opportunity to buy bitcoin at a low price, and therefore keeping bitcoin for 3 years will be very profitable.
If it's based on past history, then it's definitely profitable but about the future it's a hope that might not be certain. As you said,
No one knows what will happen in the future. So therefore, everyone who wants to invest should first consider the risk for the amount of money can afford to lose because the first point is that no one knows the future even if we are absolutely sure that there is good potential for repeat.
It all depends on how much you invested, the amount for each month, and the return on it.
The percentage is the same, but the size of the profit depends on how much funds the OP has.