I work in the film and television field. When it comes to bulbs, its kind of a big deal to be aware of how you handle them. use golves, wipe them clean. basically, you just want them to be oil free and clean before you fire them up. Im just speaking from experience. im not a bulb engineer, but maybe this will help......
...."The thin film of oil left on the glass changes the thermal characteristics of the glass. When the bulb is turned on the glass undergoes pretty significant thermal stress as it heats up. A patch of the glass with an oily finger print on it heats up slower since the oil has to be vaporized or burned off. That creates a large amount of thermal stress in the glass. It doesn't take much stress to shatter the glass or create a hairline crack.
A cracked bulb won't last long since the inert atmosphere that it is supposed to be in the bulb escapes and is replaced by air. A light bulb filament will only last a second or two in air if power is applied.
Usually the admonition to touching the glass of the bulb is for high power lamps like quartz bulbs or the bulbs used in projectors. Those high power lamps generate a lot of heat, and therefore a lot of thermal stress in their envelopes, when they are on. "
