Of course it is possible to bank too soon. Any points you bank now won’t be available until next year. If you suddenly decide to take a trip this year, you will have to Borrow points from next year. That gives you flexibility, but borrowed points and banked points are not the same.
If you change your mind and end up cancelling the reservation:
Borrowed points that are unused, will expire at the end of this use year. And there is nothing more you can do with them, if you can’t use them.
Regular points that are unused could still be banked, if before the end of April, or TRANSFERRED to someone else, and THAT PERSON could bank them, even after the banking deadline, and right up to the end of the Use Year! This gives them some potential value.
Meanwhile, Banked points you move into next year MUST be used by the end of next use year, or they expire. You cannot Borrow them again, Bank them again, or Transfer them, so you have less options, making them, potentially, less valuable.
So, is there ANY realistic chance you might use them before April 30th? If not, then bank away. ANY chance you will use them by the end of the use year? If not, then bank them. If so, then CONSIDER THE LIKELIHOOD OF A TRIP THIS YEAR, and either Bank them, then Borrow more if you actually do end up needing them, or don’t bank them and Transfer them before the end of your use year, to someone who can either use them or bank them, and might pay you money for them.