|It makes sense to keep a spare lamp on hand because you never know when you will need it—until you turn on the projector. You might be preparing your quarterly presentation in the executive boardroom, warming up for a sales pitch for your most important customer, or sitting down to watch a film with your family.
Suddenly the excitement of being prepared is interrupted by the realization that the lamp in your projector is just a little too old, or maybe it was damaged during your recent trip. If you have a spare lamp, you can change it immediately. Problem solved!