All kids are different...
My DD1 well and truely stopped doing it before 2yo.
My DD2 is currently 2yrs,8m and still doing it...

although admittedly, she has been much better the last month or two.
I am hoping DD3 stops early as DD2 does our heads in!
If she can get her hands on them, she still eats crayons, texta nibs, paper, plastic, gumnuts and other seeds/nuts from outside and dirt but just not as much as before LOL. She mostly just chews on them and will spit them out if catch her and ask her to.
Good luck with your DD