If you have long-term clients with whom you have great relationships, it may pay (literally) to occasionally introduce someone new into the relationship so they can ask the ‘dumb’ getting to know you questions, based on psychology research from the Cialdini Inside Influence people. While they have moved the link, the research is outlined in The Small Big,
The original title was Older? Yes! But Wiser? Maybe Not!
The research was done on personal relationships, but they make a case for the sales and business applications towards the end of the article.