Grit and how long

[ClayCraft2000]

I got my first egg from my RIR's yesterday and I started giving them grit mixed with their food. How long do I need to feed them grit? forever? For a few months?

 

[Wyorp Rock]

Grit should be offered free choice in a separate small dish and not mixed with feed. Chickens will only eat a few pieces as needed.
You should also offer oyster shell free choice in another separate small dish and not mixed with feed. You layers will pick up a few pieces here and there when they need extra calcium.