A player who has platinum membership can set their vacation days to "automatic". This means that if a game is about to timeout a vacation day is automatically drawn down and used to prevent the timeout. This is really intended to cover for unexpected short term reasons for not being able to play - so an extra benefit for that level of membership. However if the player has stopped playing for a long time (for whatever reason) you have to wait until eventually the vacation days run out, only then will the game timeout. As I know this takes a surprisingly long time if the player has a lot of vacation days in the balance.
I hope this helps explain the behaviour of the game.