So I was rewatching some of DS9 season 7, and all the Worf/Ezri/Jadzia drama got me thinking. So you're an unjoined Trill, let's say around age 20. You get a symbiont. You live with it for 50 years, you die, and it gets a new host. Does the new host have have just 50 years worth of memories from you, or the entire 70 that that humanoid trill lived for? Essentially, does the symbiont pick up stuff that you experienced before becoming joined?
Good question. I don't know that there is a canon answer to that, it would be like Jadzia remembering things that happened to Curzon before he was joined. I'm going to say that because the host and symbiont become a shared intelligence that the symbiont acquires whatever knowledge and memories that host has, integrates it and carries it on. Like, if Torias learned to pilot before becoming joined, subsequent hosts of Dax would have the skill also.
But this is purely speculation on my part.