Sarah Johnson wrote a great article for CFO Magazine about Auditor-Client Relationships. It is interesting to note that while many relationships have changed numerous times, there are those that have lasted for 50+ years. Having long lasting relationships may help, as both the company and auditor are able to understand exactly how the company works. However, if these relationships last too long, there is the possibility for regulations to be relaxed or issues to be overlooked.
"But amid all that tumult, many unions have endured — sometimes for more than a century. The longest-running relationship on record is between Deloitte & Touche and Procter & Gamble, which has employed only one primary audit firm since its incorporation in 1890. Indeed, to crack the list of the 100 longest-lasting auditor-client relationships, your company would need to have used the same firm for more than 50 years."