We increasingly interact with multiple interactive artifacts with overlapping capabilities during our daily activities. It has previously been shown that the use of an interactive artifact cannot be understood in isolation, but artifacts must be understood as part of an artifact ecology, where artifacts influence the use of others. Understanding this interplay becomes more and more essential for interaction design as our artifact ecologies grow. This paper continues a recent discourse on artifact ecologies. Through interviews with iPhone users, we demonstrate that relationships between artifacts in artifact ecologies cannot be understood as static, instead they evolve dynamically over time. We provide activity theory-based concepts to explain these dynamics.