game of thrones - Just how many White Walkers are there?

I do recall a few instances throughout the series/books where they describe the armies of the White Walkers, but as far as I can recall I was under the impression that the vast majority would be comprised of wights, rather than White Walkers themselves.

Are there descriptions or discussions that take place that give any insight to how many actual WW there are?

We do see how one is made in the tv series, but with the age at which that occurs I am lead to believe there is either an age acceleration process that infants also undertake (they have all looked ancient as shown in the tv show) or they are taken somewhere to grow up and don't get enlisted in the army until they are 'of age', or something similar.

Answer

The official script for Season 7 Episode 7, "The Dragon and the Wolf", has been released because it is up for an Emmy. In that it mentions that there are hundreds.

EXT. EASTWATCH, NORTH SIDE OF THE WALL

Emerging from the frozen coastal forest, the ARMY OF THE DEAD comes in force. All of them, 100,000 strong, with hundreds of WHITE WALKER officer corps on their dead horses

_{Game of Thrones, Season 7 Episode 7, "The Dragon and the Wolf"}

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I believe that the most we see on screen at once, though it's unclear if these are White Walkers or wights but I believe them to be White Walkers, is 12 plus the Night King. This is in the final scene of Season 4 Episode 4, "Oathkepper", when we find out what the White Walkers do with Craster's babies.

In the ending for Season 2 Episode 10, "Valar Morghulis", we can see 5-10 White Walkers though interestingly the effects company was told to do between 10 and 30.

“It was challenging because we only had 50 extras, which required crowd replications. They wanted about 1,000 zombies or wights, as they called them, with about 10 to 30 White Walkers mixed in, and we only had one White Walker costume that had to double for all these white walkers.
_{Fast Company, Collaboration Isn’t Always Pretty–Behind The Emmy-Winning VFX For “Game Of Thrones”}

In Season 5 Episode 8, "Hardhome", we see about 4 or 5 White Walkers on the top of the cliff and one comes down to fight Jon and is killed.

In Season 6 Episode 5, "The Door", we see what appears to be 3 White Walkers come to attack the Children of the Forest, The Three Eyed Raven and Bran and co along with the Night King. Earlier in the episode when Bran receives the mark he only sees 3 White Walkers along with the Night King.

In Season 7 Episode 1, "Dragonstone", when Bran is spying on the dead, through Greensight I believe, I count what appears to be 6 or 7 White Walkers leading the army of wights.

In Season 7 when Bran is spying on the army of the dead with his ravens I only see 2 or 3 White Walkers walking along the flanks of the wights and 2 or 3 with the White Walkers though with the way it's filmed it's hard to say for sure.

In Season 7 Episode 6, "Beyond the Wall", we see what appears to be four White Walkers with the Night King after Jon Snow has just killed one.

It would appear their numbers are into the double figures but as to an exact amount we do not know.