Well, this forum structure is pretty similar for quite a while, but I would say that Lugano 1956 - Oslo 2010 can be used for more general discussions.
ESC subforums (e.g. ESC 2017) are more used for general discussions about that edition (e.g. http://escunited.com/forum/threads/...gulation-system-would-have-stayed-(2004-2017)), but those are threads that were created in the general ESC chat subforum for that edition while it was active (Jamala's Jukebox in this example), so we decided to keep the threads that were created during that edition in the original subforums.