In the last update on the TT2 Update Log thread from July 30th, by Astor he wrote:
New features:- now abandoned countries will removing from the game. The country is counted as abandoned if player not enter to the game by appropriate country hero for (7 + hero level / 2) days.
What does (7 + hero level / 2) days mean? Is that 7 days plus the hero level so if your Hero is level 30, it is 37 days or 67 days or just 7 days. Just wondering how long of a vacation I can take. Love your game.