PPPs-and social PPPs in particular-tend to unfold over the long run. Thus, it is essential to evaluate success on a long enough timeline that short term expenditures don't influence future decision-making about the validity of the project.
Often, the longer timelines on which PPPs are laid out do not fit neatly into an annual budget, and fit even less neatly into the political cycles governing democratic governments. Many PPPs require longer timeframes in order to see returns, but this doesn't mean that they are not worthwhile. On the contrary, large projects like these can have an outsized impact, but it is crucial to develop a framework for evaluating them on their own terms to properly understand where success or failure actually lies.