This chapter looks back to learn from experience, and also looks forward by describing a simulation modeling approach to planning for future growth and change. Significant aspects of the infrastructure model for hospital planning were anticipated in the 1960s and 1970s the British architect John Weeks and the architectural practice Llewelyn-Davies Weeks Forestier-Walker & Bor. It is valuable to examine how their designs have adapted to growth and change over a 40+ year period. Their most ambitious project was Northwick Park Hospital in north London, which followed their ideas of “indeterminate architecture” and “multi-strategy building.” It remains in use and the experience of adaptation at this site is reviewed. In 1973, while Northwick Park was being completed, the practice undertook a research study that included a modeling exercise to compare the way that seven distinct hospital planning types could adapt to a defined set of scenarios for change. The capital costs and costs of change were estimated. It questioned whether the higher-cost strategies with complex provision for physical flexibility would provide good long-term value. The modeling in the 1973 study was hand-cranked in pre-computer days, but it represented a highly effective approach to strategic decision-making in situations that are subject to future uncertainty. Today the approach can be updated with computer simulation, allowing thousands of scenarios to be explored instead of the handful in the 1973 study, as shown with a worked example. Even a sophisticated simulation model requires well-judged and realistic input data, and this relies on experience from Northwick Park and many other examples of case study research.