You should have absolutely no problems whatsoever securing a ticket this far out for EZE travel.

I just booked yesterday flights EZE-SFO for Dec/Apr. No problems at all finding availability on my first choice of dates. Direct TACA booking was easy. GP was happy to get the reservation. They now call TACA with the ticket number (a step in the process we used to have to do ourselves.) I received an email this afternoon saying the ticket had shipped via UPS already! Great service these days from GP! Not only that, the new integration of the website with customer information as well as award booking information is fantastic.