Architectural stability refers to the extent to which a software architecture is flexible enough to respond to changes in stakeholders? requirements and the environment. We contribute to a novel model that exploits options theory to evaluate architectural stability. We describe how we have derived the model: the analogy and assumptions made; its formulation and possible interpretations. We use a refactoring case study to empirically evaluate the model. The results show that the model can provide insights into architectural stability and investment decisions related to the evolution of software systems.