Please note this post is about a specific fi-7160 Fujitsu Scanner. Your Fujitsu scanner might be a different model, but it should be similar in many respects.
It's really a simple concept that you need to understand. Imagine that you wear glasses (if you don't). Your glasses need to be cleaned daily to see properly. They get dust and smudges and so on. There are lenses inside your scanner that need to be cleaned often for good performance. Merely taking a swab and a pad cleaner from the Scanaid cleaning kit and wiping down lenses, pads, rollers, etc. every so often will keep your scanner in top form, and it might take you all of 30 to 60 seconds!