I went back to my main world recently and portaled to an old base that I built in Mistlands. Although the full Mistlads plants, etc did not spawn there, the terrain definitely has changed.

https://steamcommunity.com/sharedfiles/filedetails/?id=2909696604

The portal was burried in the hill, so it was destroyed just after I got through. Fortunately all the mats from the destroyed building contents were sitting on the hill/roof. Unfortunately I couldn't remember the name of the portal, so I couldn't activate it when I rebuilt it.

There were enough mats to almost make a ship (I assume there wasn't a ship in there when the terrain changed, since I didn't find any ship mats), but no ancient wood or deer skin, so I couldn't make either ship. Fortunately there was a small black forest and swamp not to far away, so I was able to get the wood, build a longship, and sail to another nearby mountain base.

I have a couple more mistlands bases in that world. One is my Mistlands bar and restaurant in the tree tops, which I already verified is still there, and one inside a tree, which I'm now afraid to go to. :-)

I'll be more prepared next time!