I was under the assumption that the Places of Power were not missable, as they are mostly tied to simply finding them in the world. Some required you to be at a certain part of the story quest to be reachable, but even if they were missed during said quest, you could seemingly go back and find them for the skill point afterwards. However (late story quest spoilers):
In the quest Through Time and Space, there is a Place of Power in the second location. It is the locale after the Ddiddiwedht Desert, the first you are separated from Avallac'h, with the poison gas. The Place of Power is pointed out, and told how to navigate to, in this Eurogamer article. However, it doesn't appear on the map, and could be missed depending on how you progress through the poisoned, lowlands areas. Obviously, if you don't activate this Place of Power before moving on to the next world, you will permanently miss it.
Are there any other instances of permanently missable Places of Power, due to either story, quest, or geographic limitations?