Nowadays, a central issue for applications executed on heterogeneous distributed platforms is represented by assuring that certain performance and reliability parameters are respected throughout the system execution. A typical solution is based on supporting application components with adaptation strategies, able to select at run-time the better component version to execute. It is worth noting that the efficacy of a reconfiguration may depend on the time spent in applying it: in fact, albeit a reconfiguration may lead to a better steady-state behavior, its application could induce a transient violation of a QoS constraint. In this paper we will show how consistent reconfiguration protocols can be derived for stream-based ASSISTANT applications, and we will characterize their costs in terms of proper performance models.