Hi dtsantos, welcome to FT.

Depending upon the carrier, flights may only be booked up to 330/353 days in advance.

I had this issue in March when I needed to book an xONEx for travel between June '08 and May '09, including April '09.

I booked the June flights straight off and used dummy dates for the May and April 09 flights (Nov, Dec). After returning from my June excursion, I called and re booked the remaining flights to their "correct" dates.

I did this with AA, no fuss, no additional cost, no problem.

There should be no additional cost in booking close to departure date, the main issue with that is finding the avalability in the required fare buckets (A, D & L).