There are different kinds of stability. One is whether the same language is spoken informally. Another is whether people are able understand earlier texts. I'm pretty sure texts from the 20th and 19th century are commonly read in High School, TV shows from 1960s onward are watched, etc. Having the past ever-present makes it something current informal language relates to.

Many, many people speaking English also creates an incentive for stability at the same time it creates variation.

I have a book from the 1700s on my bedside table I can read just fine...

My lived experience is I can read texts from hundreds of years ago just fine. Old mate is struggling with 50s tv.

The only tip is to use stable language. IE don't use the term dab or vibe or whatever the latest fad niche speak is.

I think whoever is interested in a 500 year old website is going to be ok.

This comment will be fine in hundreds of years. I completely expect (at least Australians) to continue to use “old mate” for a long time to come :).

Thats the difference right ?

One is a 'phase' the other is cross generational.

> The only tip is to use stable language. IE don't use the term dab or vibe or whatever the latest fad niche speak is.

Stuff like that can easily be looked up though, there are a number of "youth/hipster speak" dictionaires, pages like KnowYourMeme...

Or picked up pretty easily. P. G. Wodehouse and Arthur Conan Doyle use some anachronistic language but it’s still 99% understandable without a dictionary.

I don't think it has evolved much at all. New words, yes, and some words fell out of favor. But you can find a book written in the 50s or a movie from the 50s and you would have no trouble understanding it. I'm fact, without context, you likely wouldn't notice it was from 70 years ago.