My kid did this through age 5. No clue why. She did eventually give it up- not due to anything we tried, which was everything!

Still waiting at 4. Otherwise developmentally normal/ahead.

My eldest until about 2.5. Middle child, much younger, more like 18 months. Youngest is still doing it, but he's a baby.

I wouldn't worry until 3.

But I do feel you - I find that after sleep training and a good schedule at 4-6 months, the next big "life is easier!" moment is when your kids stops putting crap in their mouth and your follow distance at the park and other people's houses moves from 1 foot to like 12 feet. Ah, freedom.

My kids still do ...7 and 9. I think some kids just do this

Because DS is almost two and will not drop. Ifs constant. Other kids his age don’t seem to do this. At what point do I rule out some nutrient issue or PICA?