Well, if it is the mainland states you can state them as quickly as possible. You will still get a crapload of immigrants to boost your population so no worries! But when it comes to colonies on other continents it's much harder to state them. I have never managed to convince my population to move to the colonies in any larger numbers so. If you do manage to achieve this, make sure that the literacy in the state isn't completely down the shitter so your research points aren't hurt in the process.