Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.
There are really only two advantages to using just a single lens. One of them is creative. Keeping one set of optics mounted on your D5100 all the time forces you to be especially imaginative in your approach to your subjects. I once visited Europe with only a single camera body and a 35mm f/2 lens. The experience was actually quite exciting, because I had to use a variety of techniques to allow that one lens to serve for landscapes, available light photos, action, close-ups, portraits, and other kinds of images.
Of course, it’s more likely that your “single” lens is actually a zoom, which is, in truth, many lenses in one, taking you from, say, 16mm to 85mm (or some other range) with a rapid twist of the zoom ring. You’ll still find some creative challenges when you stick to a single zoom lens’s focal lengths.