Should a page's GUID be the same in all languages?

In our current site, we have 4 languages configured.

- English (Primary)
- German
- Japanese
- Chinese


My assumption is that the PageSiteNode.PageId, PageSiteNode.Id, or SiteMap.CurrentNode.Key values will be the *same* as I navigate to each language for a given page.

Am I incorrect in assuming this?  We are seeing that these GUIDs are changing from language to language for some pages.  

Is there one that is reliable?  Also, is there one that is reliable for the lifespan of the page, no matter if you change the page's properties and/or content?

Thought this would be a fun exercise, but running out of time to see how it actually ties together.

With regards to 'some pages' changing and some not, that's depending on whether a page is 'synced' or not. The synced ones have the same, the non synced ones differ.

As for how to robustly retrieve a root/parent 'synced' guid, have no idea atm, sorry...

But first testing with .IsSplitPage, Then retrieving the cultures and their latest content_id, val, seq from [pg_dt_published_translations] should do the trick.

J.