As we all discover eventually, age is going to be accompanied by declining eyesight. If you make your living writing and coding, this is going to result in some discomfort as it becomes harder and harder to read the text in books, newspapers, or your screen. You can’t do much about printed matter except to get stronger reading glasses but if you’re an Emacs user—or, really, any other editor—it’s easy to increase the text size on your screen. I find myself doing this more often when writing, especially at night when my eyes are tired.
The problem is that the adjustment doesn’t persist across sessions and you have to make the adjustment for every buffer that needs a non-default font size. James Cherti has a solution: persist-text-scale.el.
The TL;DR is that once you set a new font scale for a buffer, it persists across sessions and furthermore you can arrange for all buffers of a certain class to have the same scale settings. That’s perfect. You can, for example, arrange to have all the buffers you use for writing or reading text be in a larger text while keeping other buffers in the default or even smaller text.
Take a look at the GitHub repository linked above for the details. You might also want to check out the comments in Cherti’s Emacs subreddit announcement where he answers some questions on what he’s trying to accomplish with the package. If you’d like to have certain buffers rendered in a larger (or smaller) font, this package may be just what you need.