Upvote:1
When you apply for the visa, you submit a premise for your trip and an itinerary. You can adjust your travel plans slightly later on, but itinerary must be truthful at the time you make it.
The visa may be granted for a few more days at either end. If so you are not required to extend your trip. In fact, it is your responsibility to abide by the terms of your visa, and it never hurts to have a day or two extra in reserve.