Electrical

You could have a door jam switch sticking or a problem with the delay timer under the dash.

I can make a suggestion based on my Chrysler experience. They used a thermal timer that plugged into the fuse box. It was silver and about the size of an old florescent bulb starter. When the lights have been on for half a minute or longer that unit will feel warm. They had an extremely low failure rate so any one that you might find in a salvage yard stands a real good chance of being good. You could also pop the cover off and clean the contacts with some fine sandpaper.

This one uses a lamp control module.