Hi Gaspar,
Your post is quite pertinent and addresses an issue that many organizations face. And yes, there is a process to effectively apply lessons learned. It's called "Continuous Improvement" and more and more PMOs are adopting it as a post-closing process step. The reasons and need for this are quite clear and you cited many of them.
The Continuous Improvemment process step is performed by the project manager after project closing. Like Mr. Welch mentioned lessons learned should be amassed throughout the project life cycle. And, after completion of the project, the project manager executes the Continuous Improvement process step. The objective of the Continuous Improvement process step is to prepare and submit a Continuous Improvement Recommendation based upon the project experiences and lessons learned of the project.
Thus, lessons learned are not file and forgotten, rather the organization such as PMO receives the Continuous Improvement recommendation. For small improvement opportunities, that recommendation can be submitted to the PMO by the project manager without necessarily even having to meet. For large, significant improvement opportunities, the project manager may need to formally present the recommendation as well as include others that can help communicate the lessons learned problem, alternative remedies, and recommendation. From that point, it is up to the PMO, management, and the leadership team to handle as appropriate.
Continuous Improvement and committment to a culture of Continuous Improvement is the way in which organizations get better, not "hiring and firing" nor "hope and prayer" though these things are regrettably to common.
While PMI has done an exceptional job in so many areas and the Guide to the PMBOK® is an outstanding work, it doesn't address very effectively (nor is it intended to) the many processes and policies that any PMO or project organization needs to put in place in order to manage and continually improve the organization. Continuous Improvement is but one of those things..!
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