A key question in the literature on payments for ecosystem services (PES) is how payments incentivize conservation action and, in particular, how they interact with other motivations, including motivations for environmental stewardship. Related to this question are concerns about the temporal sustainability of PES: what happens when payments cease and whether a ‘no pay, no care’ environmental ethic is fostered. I present empirical research from a case study in western Uganda, where forest-adjacent communities are paid in exchange for planting trees on private lands, for carbon sequestration. The study demonstrates the range of values people have for trees in the landscape and the range of motivations for participating in PES schemes. However, the analysis shows that payments are clearly the main motivation for involvement, except in one area where people are more motivated by aesthetic and existence values for trees. Given the widespread importance of money in motivating involvement, I investigate the profitability of participation over time. This profitability analysis, in combination with qualitative data on perceptions of, and plans for, the future, contributes to understanding the temporal sustainability of PES. I draw on various strands of evidence to argue that the way participants prioritize payments may constitute a threat to the long-term maintenance of PES activities, particularly in situations such as in this case study, in which there is a mismatch between payments and contract length.