First timer looking for a deal!

My family has decided to take a cruise next January and they’ve already booked. I’m looking for the best deal.

Is there a better time of the year to book a cruise? Should I risk and wait until we get close to sail date and then book?

This would be a four people (including myself) so we do need the 4 person room. Ship is Icon of the Seas.

Thank you all in advance for any help!