Pension products and long-term insurance policies play a crucial role in our societies. This talk explores approaches for their cost-effective production through investments in financial markets. The key tool here is to link financial and insurance strategies to an appropriate fundamental theorem. To address the risks and uncertainties inherent in such investments, we draw on methods from financial mathematics and the framework of Knightian uncertainty. We will discuss recent developments in this field, highlighting their implications for the sustainable and resilient structuring of pension and insurance products.