Scientists, policy makers and non-governmental organisations, among other actors, increasingly recognize the relevance of conducting research through citizen science (CS). As such, new projects involving this practice continue to emerge. Participants in CS projects can be engaged in various steps, which can range from contributions in designing the projects and defining/prioritising hypotheses, collecting, and analysing data, to communicating the results. However, as with other research practices, CS faces several challenges and questions that need to be addressed such as the recruitment of participants and their retention. Since retention of participation is central to the success of projects and their overall impact, a better understanding of the specific actions that increase such retention could benefit the citizen science community. The NEWSERA project (https://newsera2020.eu/), is analysing how to improve engagement of each stakeholder from the quadruple-helix model (citizens, academics, policy makers and industry) in CS through the implementation of co-created innovative science communication strategies. So, in a dialogue roundtable that took place at Engaging Citizen Science Conference 2022 (Aarhus, Denmark), the NEWSERA team developed a methodology to discuss with CS project managers, participants, and other stakeholders, the challenges faced in maintaining long-term engagement, specifically focusing on citizens as the main stakeholder target group. The discussions and results that resulted from this session contribute to the debate around the best strategies to engage and keep participants in CS projects and provide some clues for CS project managers to improve their engagement strategies.