Just yesterday, I noticed my bedroom walk-in closet light fixture was not operating properly. Turn it on, sometimes it works and sometimes doesn't. This is keyless type and has been in the house probably more than 30 years. Well, upon a little investigation, I finally see the little tip down in the bottom has a hole burned in it. So, when I moved the light bulb around, it made contact, but would not maintain contact. The house has an attic fan, and was used many years before we bought the house. We used it a few years, then added central AC. But the vibration of the attic fan would cause the incandescent bulbs to go out very quickly. After central AC was installed, the bulbs lasted much longer. My next step is to replace the fixture, with something a little better than a keyless.