I have bought two "12V Timer relay" on eBay for 4.35$US each.
Here is a picture:
Here is the diagram I have made just for you:
On my Fleetwood, I have install one relay for the Docking Light and another one for the Utility light (compartment lights).
When I turn the Utility light switch on, the lights are on as usual and forever until I turn the switch off. But when I turn the switch off, the lights stays on for a few minutes. I can program the relay from 0 to 60 minutes. I have chosen 15 minutes for both of the Utility and Docking lights.
I did it because my kids forget to turn off the docking lights or the utility lights all night long. Now when one of my kid will go in a compartment they will simply turn it on and off and have plenty of time.
I put the relay just beside the Utility Light switch behind the dash. On the switch there are three wires. One of them is +12V and is live all the time. The other two are use to turn the lights on.
On eBay item number 390532577881. Click here
The Relay Timer 12V I have used is 5A. 5A is enough in my case. All my bulbs are LED which require low amperage. I changed the fuses to 5A in the electric panel.