Mouths

Do your little ones still put everything in their mouths? It's getting less but he still puts most things in his mouth. We went to a friend garden today but I had to stop him from eating sand, and putting stones in his mouth most of the time! Do you stop them from putting things in their mouths? I obviously stopped the stones but most stuff I let him chew on but not sure if I should try to stop this as much. When does this start to stop?. Thank you