This is close, and I'd grant that limit trips are associated with longer run times. But in principle continuous furnace run time shouldn't cause a high limit tr

This is close, and I'd grant that limit trips are associated with longer run times. But in principle continuous furnace run time shouldn't cause a high limit trip. The limit is mainly to protect the heat exchanger from damage. The primary cause is usually low/reduced airflow, although bad sensors are also common. A high limit trip will generally cycle the furnace off for a time period. Somewhere between 3-5 off cycles will result in lockout and the furnace will stay off. The control for this is more likely to reside in the furnace board vs an aftermarket ui.