Making training stick after the certificate is issued

Most of what is learned on a two-day course is gone within a month unless something in the job requires it. That is not a criticism of the course; it is how memory works without retrieval. The things that seem to help are small and unglamorous: a task the learner has to do with the new knowledge in the first week, a supervisor who asks about it, and a short refresher at a spaced interval rather than a year later. What does your organisation do between the certificate and the refresher, and has any of it been measured?