Ask if you can publish their testimonials. In addition, satisfied customers make the best sales staff. The more money your associates earn, the more work they will put in on your behalf. This is why you, as an Associate Program owner, can afford to give an associate a lot of money. You're not looking at immediate maximum profit.
Many marketers make the mistake of attempting to maximize the profit up front.
You can take advantage of your customer's satisfaction by selling back end products to your existing customers. Many of my best customers came as a direct result of free support services I developed for them over the last few years. Excellent customer service is a must. Don't try to make money on everything you do. Instead listen to what your customers are telling you.