Oh, it can be really fast. If the new government have other interests or change their minds.Long range geostratic interests of nations are not really directed by the coming and going of prime ministers or presidents.
Just look at the pkk and the greater middle east agenda, didn't matter who was president the exact same agenda has played out across all presidents irrespective of who came and went and what ideological divide they sit on.
But if you really want to know what a nations policy is towards you, pay attention to her media. That's where the true face reveals itself. Worth keeping in mind that no prime minister or president of any western nation could win an election unless the media supports it.