I one year we can plan our trip 2 or 3 times.
Just kidding.
Basically we plan our trip 3 to 4 months ahead.
But we do not arrange excursions etc.
The only thing we plan is the hotel/apartment, and the flight.
A few weeks before we go we contact the rental company for scuba diving gear and we make a reservation at our favorite restaurant. (Just in case)…
But we never stay in the resorts, I do not know if you have to plan these kind of arrangements earlier.
Good luck.