Some of my posts are long. My longest post is almost 20k words as of right now (60-80 pages printed out), and will get longer as I update it.
Length is an imperfect yet useful measure of the amount of detail one can expect. There are many “lists of practices” on the Web about web design. By communicating that mine would take an hour and a half to read, I communicate that my list has some more thought put into it.
This also signals to some people that they should probably bookmark the article for later so they can read it properly, or helps them prioritize shorter articles first.
Someone who may end up reading an entire post after going through a paragraph or two may be scared away if they know it’ll take them 30 minutes to go through it.
I think these people would be scared off regardless, simply by seeing how much they have to scroll through. They might also feel overwhelmed by the number of entries in the table of contents. That’s why I include a “TLDR” or explicitly recommend skipping from the introduction straight to the conclusion for readers in a hurry.