Dutch chapter, have a tradition of recurring conferences.
Such presentations are relevant. What was presented was the current state of affairs by the "thought leaders" at the time. Many presentations have not been recorded on video or audio but quite often the slides or a paper is available somewhere.
It is easy enough to add these conferences, these talks to Wikidata. It is relevant because it allows for lists that can be generated with a bot like ListeriaBot, it enables people to find the presentations and when they find it interesting they can even see what is available. What it also does is link presentations to the people involved. At some stage you may find how often Lydia presented and where. <grin> at this time, only once </grin>.