Handling of the bulbs and the oils causing problems is a old wifes tale. Although it has bearing, its only with lights that are not insulated with a protective jacket and have the arc exposed. Like double ended bulbs.
Sometimes if the mogul connection is not wound all the way, the base contact may not interact. Creating a open circuit. Other times this connector may deform or dislodge, so making sure proper contact is made rules these out.