Large scale and long-lived application systems, enterprise applications, require persistence, that is provision of storage for many of their data structures. The JavaTM programming language is a typical example of a strongly-typed, object-oriented programming language that is becoming popular for building enterprise applications. It therefore needs persistence. The present options for obtaining this persistence are reviewed. We conclude that the Orthogonal Persistence Hypothesis, OPH, is still persuasive. It states that the universal and automated provision of longevity or brevity for all data will significantly enhance developer productivity and improve applications. This position paper reports on the PJama project with particular reference to its test of the OPH. We review why orthogonal persistence has not been taken up widely, and why the OPH is still incompletely tested. This leads to a more general challenge of how to conduct experiments which reveal large-scale and long-term effects and some thoughts on how that challenge might be addressed by the software research community.