There is no magic number for how often you should test-the answer is different for every organization and it really depends on how you intend to approach the issue. However, many organizations will admit that they only perform a minimal amount of testing due to a shortage of time and resources.
At IR, we provide performance testing services to some of the largest banks, retailers, and enterprises in the world all the way down to the smallest businesses. Customers know the end result they are trying to achieve-we know which testing services and strategies will get them there.