My LO will be 3 in March and is still sitting in a booster at the dining room table. We have a high top table, so I haven't tried her out on just a chair yet. She sits in just chairs other places like at my parents or restaurants, with no issues. She is pretty petite though so maybe the extra height of the booster is helpful.

When did you let your LO sit in a regular chair? What made you decide to do it?