Testimonials from satisfied customers are an excellent selling aid; and the clearer the testifier’s human experience comes through, the better. However, there’s such a thing as overkill. One medium-length testimonial, or two or three short ones, are plenty for most sales pieces; after the first 500-1,000 words, prospects will toss your material aside.
Few people can empathize with more than one or two others in one sitting. Be considerate of readers’ mental-absorption capacity.