Generally we book about 3 months in advance, however when we decided to go to the Maldives we booked it 7 months in advance, purely because we had saved up the deposit and then had to save up for the rest of the holiday. it was our once in a lifetime holiday on those stilts cabins for 2 weeks in paradise with nowt to do other than to enjoy all the S's..
in the event, we got stiffed 11 days before departure by the holiday company who told us that due to reef conservation, we could not have what paid for and offered us the alternative of.....wait for it......Fuertaventura.....
We ended up getting our money back..but not before I had bit the bullet and stuck a holiday to Thailand on my credit card...so we went there with 11 days notice...we didn't even know what hotels we were staying at or owt. We just went to Thomas Cook and said..here is £x and we want to go to Thailand..sort it.
The Liveaboard we are going on at the end of Jan was booked at the end of September..so that is more like our usual 3 months.
We said never again that we would book so far in advance...so now we save up, then decide what we want..and if the right deal comes along.....