There is no hard and fast rule, since by the nature of any random proces, some people will come up more often than not: for example, there are some people who have won a lottery more than once, or been struck by lightning more than once. If, however, you believe that the selection process is not random *and* that you are being singled out due to a protected reason, such as your race, religion, age over 40, disability, or sex, you should consult with an employment law attorney to discuss the matter.