Mind, I'm only asking to spark a conversation. I don't expect An Official Answer.
I recently watched an "extra" from the 3rd season video release of "Game of Thrones", about the creation of the Valryian language. They hired linguist David Peterson to invent a coherent language for the show, based on fragments of it from the novels. The segment was an interview with him, and some discussion of the process he used, as well as the results.
I'm paraphrasing from memory now, so don't expect it to be fully accurate.
He took the "known" history of the Valryian empire, and invented many dialects of the original, "High" Valryian, which he likened to Latin; a scholarly "official" language not generally spoken throughout the empire. "High" Valryian has no articles like "the" or an", and uses poetic noun forms. He created "Low" Valryian to be a kind of simpler syntax, a bastardization of the "High" form that conquered peoples would be speaking.
And etc etc.
There is a scene in the show, 3rd season, where two people each speak what I'd assumed was "just Valryian" when I watched it. However, David Peterson explained that one of them was actually speaking "High" Valyrian, and the other, "Low".
When he walked through the differences, line by line, in what they were saying, it became obvious that they were speaking slightly different languages. Their words for various nouns were subtly different, though they could each understand the other.
But did I catch this watching the show? No, in fact, I assumed that the actors were speaking somewhat random sounds, because the subtitles with the same words in English, DIDN'T sound the same when spoken by each actor.
And this makes me wonder, how much effort is sensible, when world-building? For me, the viewer of this show, his efforts were somewhat wasted. While I love the way any (there are many) of his dialects of "Valryian" sound when spoken -- the actors do a fine job with it -- clearly he could've stopped at the one language and called it a day.
So, how much world-building do you like to do?
At one end of the spectrum, is "none" -- our stories are really just 21st century Americans (or, whatever country & culture yours is) "in space" / "with dragons".
At the other end of the spectrum are efforts like Tolkien's, or David Peterson's on the Valryian language, with huge swaths of invented history and much fine detail.
Are we world-building to satisfy the average reader? Ourselves? Specialists (say, other linguists) who can appreciate the polish that goes beyond the obvious?