I had an oil burner in our basement that was slow to light, altho it did light before the timeout timed out. Whenever the burner did not light immediately, when it did ignite after a few seconds, it was with a whumpf!!! that you could hear upstairs. That was how I knew it was time to readjust the ignition points where the spark was formed/located that ignited the oil.

The spark had to be in a certain position with respect to the fan/cone shaped oil pattern out of the oil nozzle. Due to vibration and actual wear of the metal points, an annual adjustment was generally necessary. After the first service call, and watching the repair man closely, I was able to do the positioning myself. But, it was good to have that backup timeout just in case.