I'm not a member of any ST program but it turns out I'll be using China Eastern and probably other members too soon so I decided to sign up. I flew Rio - Buenos Aires - Sydney with Aerolineas Argentinas so that should be a good amount of miles to start with but what airlines will take them 2 months retroactively? Delta's policy says 30 days, alitalia's website is a mess, and AR doesn't accept any miles before you signed up.