Flexible Travel - Timing on airfare purchase?

I’m going to be traveling through some combination of French Polynesia, Cook Islands, Fiji, New Caledonia and Tonga this June/July/Aug and don’t know whether I need to book airfare in advance. I have a very flexible schedule, so I’d like to avoid it where possible. Anyone know how far in advance the flights book in advance?

My current understanding:
Intra-country flights: can book while there if you are flexible on what time of the day / a few days in either direction
International flights: I have no clue. Some people say no need but reading LP and the net seems to indicate otherwise

Well, there's only one flight a week between the Cooks and Tahiti, so you might want to book that in advance.

Last week in July and first week of August its Constitution Celebrations in the Cooks, so a lot of inter-island flights get booked full for those two or three weeks. Same with flights from NZ to the Cooks.

Around July 14 (holiday) int'l flights into and out of Tahiti get booked up, as do domestic flights.

Domestic flights in Tonga---it's hit and miss, but I'd book in adance as schedules change at the last minute, and if you have a confirmed res. you're in better shape and won;t get bounced.

Regarding international flights:

Have you considered the entry requirements, some countries may require a ticket home or two stops away.

Have you considered the infrequency of flights (example: one flight a week from the U.S. to Tonga)

the complications of getting from one country to the other (example:Tahiti to Fiji via New Zealand or via New Caledonia via Vanuatu to Fiji, Cook Islands to anywhere but Tahiti via New Zealand)

if you fly directly between Tahiti and New Caledonia have you checked how long you can stay in both French overseas territories without having to get a short stay visa