The optimization of a product’s whole life cycle has become a mandatory task for manufacturers seeking to deal with circular economy requirements while gaining competitiveness in the market. In order to achieve such a sustainability goal, alignment of production, distribution, and field service activities is needed. In the literature, numerous studies indicate the product–service system (PSS) approach as one of the most promising business models to combine the needs of manufacturers and customers in an efficient and effective manner. However, PSS solutions aimed at practically optimizing supply chain management have scarcely been addressed. In order to reduce this gap, the current study proposes a procedure based on the PSS Functional Matrix, the Screening Life Cycle Modelling (SLCM) method, and stock management theory to optimize aftermarket services based on market demand. A case study in the medical equipment sector, where market demand can fluctuate during the contract period, is presented. The analytical results show beneficial effects in terms of both costs and environmental impact, suggesting the need for further research to augment knowledge on PSS and supply chain management. In particular, the PSS allowed the company to customize the manufacturer’s business model, adapting the supply of aftermarket services to varying customer needs.