If you book through Couples, you can book now and if a better deal comes along and it is greater than 45 days out from your stay, then you can cancel and rebook without any penalty, but any 'extras' (resort credits) you received with your original booking does not carry forward with your new booking unless those 'extras' are being offered with the new deal.
If you are booking through a search engine or a TA, then you need to check with them on their cancellation/re-booking policy. Most do charge a fee.
Juliann & Jeff
Jamaica Soon Come