Hidding from enemies (raids)

[Vampara]

It would be awesome, that there will be some kind of time duration before the enemies will find your base and when they will find, then they will attack you randomly up to the story teller and difficulty... but the idea of moving the colony elsewhere would give you time to hide from the enemies for some time and maybe if you will destroy their nearest base, then the discovery time duration could raise up and you could "buy" one year of peace for yourself.
From the beginning you have time to settle down before they will find you, after that, they will start their raids, if you will destroy their base, then you will buy you some time. It's some kind of challenge and force for player to actually attack their bases.

What do you think?