This is a dynamic question. There's been times where park passes have been booked full 2 months in advance down to now where only a week out only some parks are full. However, by May, I could see a lot more international travel picking back up, so it could be a busy spring and park passes may fill up further out. If you're wanting to wait as long as possible, I'd keep an eye on reservations and when April starts to fill up, expect May to follow soon. This would be the last opportunity to ensure you get your first choices.
The other hand would be the ticket prices. The longer you wait, the more likely ticket prices are to go up. If you're trying to get tickets through a third party site, you'll most likely have some time to get tickets at the old pricing structure, so if you hear prices went up, then you would probably want to get yours immediately while those are available.
If you're going through Disney for tickets, any reason you don't create a resort plus ticket package? You get the tickets tied to your account, can reserve your parks, and not have to pay in full until 30 days out