Software development has evolved to incorporate reusable components. A parallel development has been the availability, through the world-wide-web, of data, transactions, and communications. These developments have led to the emergence of web-services. In this context, the self-healing attribute is of great relevance: How does an application learn that a remote service has become unavailable? As the time to replace a service may vary considerably, we consider the relationship between service replacement time, the frequency of failure monitoring and the percentage of failed service calls. Extensive simulation results are presented showing the relationship between these variables.