In developing countries of the Asian monsoon region, participatory irrigation management (PIM) was introduced in the 1990s so that farmers rather than government staff could be partly or wholly responsible for operating, maintaining and managing irrigation projects. Whether or not farmers continuously participate in maintenance activities depends on the degree of their willingness to perform such activities. This study reviews the objectives, achievements and significance of a series of our six research papers that use a range of methods to increase the willingness of farmers to engage in maintenance activities, and also summarizes future perspectives of PIM sustainability. The results of the research papers showed a practical method and a new perspective for an efficient increase in the willingness of farmers; firstly by choosing factors with a new indicator, “maximum effective number of target persons”, and then improving details of how the chosen factors were encouraged by adding an incentive perspective with “no decrease in vested benefits”. Conversely, to simplify the questions regarding the selection of encouraging factors, the papers disregarded conditions such as the time and cost required for encouragement. The first priority is therefore to clarify the content of incentives based on factors that should be encouraged. Second, the findings of the papers cover only the most fundamental factors associated with PIM sustainability. Therefore, to effectively and efficiently improve PIM sustainability, there is a need to analyze “factors other than willingness” that influence the inclination to engage in maintenance activities.