I find this very helpful and generally only book HH vacations when I can point stretch:
http://hhonors1.hilton.com/en_US/hh/rewards/psdates.do
Lets you use less points for certain times of the year. If you play around with it you can generally find something that works for you. Unfortunately I do not see Bora Bora in there (Maldives I do though) so this post may be moot.