@mrmhendrix - PlaceID is a unique identifier for an entity. I wouldn't expect it to change, ever!
But rather than offer an uninformed opinion, I thought I should look it up. Apparently, "Place IDs may change over time."
From
Place IDs | Places API | Google for Developers
From the same document: "It is possible for the same place or location to have multiple different place IDs."
The document recommends that if you save place IDs, you should refresh them if they are more than 12 months old.
And if you find that your saved place ID doesn't return a result, you need to find the new ID.
See
Save place IDs for later use
Now for an uninformed opinion!
I could see a scenario where an algorithm finds a place and assigns a place id: 1.
You find the place on Maps and record the place id: 1.
Later, the algorithm finds that place again using a different path and assigns a new place id: 2.
Now the place has two ids: 1, 2.
An algorithm that keeps the data clean realizes that 1 and 2 are the same place so place id 1 is retired. The entity now has one place id: 2.
And your recorded place id, 1, is no longer valid.
That's just an idea.