Some project-based organizations report and share knowledge through lessons learned in order to improve performance in future work. The objective of this study is to test whether the use of this technique, in Project-Based Learning, is sustainable over time. Also, it is interesting to test what are the types of lessons generated most frequently, whether they have interest for the learners, and whether the activities involved are satisfactory for them. The research is carried out by incorporating the lessons learned technique into a Project-Based Learning experience over several years. The methodology consists of the analysis and classification of lessons, published in a blog, and the data collected about the students (grades and opinions). The results show that technological lessons are the most numerous and visited, followed by methodological lessons in terms of generation, and work organization lessons in terms of visits. Moreover, the opinions of the students are very positive in all activities related to the dissemination, generation, learning achieved and usefulness of the lessons in a fairly unanimous way. In conclusion, the lessons learned technique serves as a good complement to reinforce Project-Based Learning, enabling students to acquire knowledge, perceive its practical usefulness, and express satisfaction with the activities involved.