If you have an Apple store near you, waiting til near the end of the year to buy it is fine since you can carry it in and get support anytime in the first year. But if you don't have one nearby consider that the factory warranty for the first year covers all hardware problems, but only covers free call in support for the first 90 days of ownership. Because of that if you wait until the end of the year of ownership to buy Applecare, there will be a gap when you will not have free phone resolution of problems from day 91 to day 365 (or whenever you purchase Applecare).
So you can see that if you buy it in the first 90 days, your phone will be free at any time for the full length of the Applecare contract, so no gap.