Every drip tip will have some build up and left over vapor on the sides.
The good thing about the TFV4 tip is that instead of slowly building up and dripping into your mouth it usually drips out the central tube and into the "airflow tube"
Personally I keep the airflow on that thing completely closed, it simply drains flavor for no real benefit imo (if it's too hot I'll turn the wattage down). So what I use it for is exactly this, keeps my lips from getting all juicy. Then once there's enough build up that it's an issue, I open up the airflow and take a tissue and plug the bottom side of the drip tip and blow into it expelling all that buildup out the airflow into the tissue.