This document discusses the use of safety case architectures throughout a project lifecycle. We show how the early development of such safety case architectures can be used to provide a framework for the ongoing development, refinement and monitoring of safety requirements and properties. In this capacity, safety case architectures offer a way to allocate responsibility for satisfying safety requirements across the multiple stakeholders in the project. Furthermore, they enable ongoing monitoring of safety development. This means that issues such as unjustified assurance deficits (informally, unacceptably low confidence in the safety of the system) are identified and addressed early in the project.