half month one sounds wonky and depends on specific schedules, likely not a good idea. Even without much time, the 12.99 sub is fine, its not much for a months entertainment....

Lifetime subs have been proven to be very bad for an mmos long term health. SE doesn't need the burst of money they give, funding is not an issue in FFXIV, so it would only offer a very short term gain and if the game is long-lived, and big long term loss.