How long is too long for a turn?

[zap]

Not sure there is a specific time limit. I suppose after a month or 2 you have no response may be they have disappeared. However, I have 2 games going where my opponents have not sent a turn. one game for 8 months and another for 4 months.
In one case the player told me what was happening. So I wait.
In the game of 8 months I read here on the forums it is life issues. In the last case I could call the game but the player has a perfect winning record. I don't want to give him a loss by default.