Note that defdev does not publish it's slidedecks for off-the-course use by the attendees. We believe that slides are not a medium which one can use to maintain her knowledge and skills, even if it can make one to recall the moments of the training. Instead we craft other materials that our students can use as a reference to find the topics learnt, can use to locate the authoritative sources of the secure development knowledge, and some resources to practice on their own.
Thus for every course we prepare a unique "[i] for students" document. It's a google document accessible by a unique hash URL. This document persists along the lifecycle of the course: it contains the properties of the course including the location and dates, the prerequisites and how-tos if custom installations are required, and also the above mentioned knowledge (link) base.
It also worth mentioning that following each training we ask our attendees to fill in an anonymous feedback form. The summary of the feedback we share with the client.