I am wondering about the time grit remains in the gizzard once ingested by the bird. Do different grit materials last varying times before they exit the body? Is that why granite grit is preferred as it is stronger and likely to remain in the gizzard longer than other grit particles? It makes sense that the type of grit particle would influence the time it is useful for grinding up food; strong, hard pieces last longer while softer material is crushed and eliminated quickly. Does anyone have info on this matter? Thanks for your time!