What kind of grit, I think most of the "Grit" is crushed rock and will help them process and digest feed, but will not provide calcium which they need for egg laying. We provide grit year round, but oyster shell only during laying season.
I almost provide Oyster shells all year. I give it to them just before and during laying season, I give it to them when my male has molted all his feathers and I continue giving him oyster shells until he is done growing his train.