My DD took ages to grow out of this - she was a shocker. I had to do a full scan of any room she was in for things that she could choke on because if it wasn't nailed down it went in her mouth. We had a few close calls too where I had to fish bits of plastic and god knows what out of her throat.

I'd say she was probably 18 months before it began to improve, and she would have been close to 2 before I could not be watching her every second we were out of the house. Around the time she started talking was when it stopped.

I think she was a bit of an extreme case though because DS is only 12 months and although he does it too, he's not near as bad.