How soon do chicks need grit?

[Real McChicks]

I've read various things- from 2 days to 2 weeks, or not until they are eating foods other than the chick grit. So- when should they get grit?
Also- how long do they need the chick starter? I got a 25 lb bag (for 4 chicks)- not sure how long it lasts or how long they need that type of feed.

 

[Katy]

They don't need it until you're feeding them something other than just starter.