With the eairly access code how many days can we play after the launch date ?

[Vaer]

What are you even asking? Early access lets you play Heavensward content a few days before it's official release date. Of course you can play after the date as well...

Grace period. People playing during early access might not have access to the actual expansion serial key (because they might not have received it depending on shipping), which means they will get locked out of expansion content if the grace period is too short.