KISSIMMEE, Fla. — Erick Aybar and Nick Swisher are well into their 30s and, after trades, find themselves with the rebuilding Atlanta Braves. As they prepare for another season, both switch-hitters are in the final years of their contracts and neither knows how long he will be around. Aybar, a 32-year-old shortstop, came to the Braves along with two pitching prospects in a five-player deal that sent young shortstop Andrelton Simmons to the Los Angeles Angels, the only organization he had ever known.