Depends.
For CoG demos, my expectation varies on whether the IF has already been published or if it’s in the process of being published.
In the former, I probably expect maybe one or two - maybe three if they’re feeling generous - chapters of the story. What’s important to me in the published CoG demo is this: does it live up to what was promised in the advertisement? If it does, I probably will mark it in my “to explore” list. If not, I’ll probably not buy it and that’ll be that.
If there’s a CoG that’s in the process of being published, and therefore has a public demo (like the CoG WiP sub forums), I’ll expect it to be similar to a beta test for a prospective title for the HG label.
In an HG demo, my expectations are looser, so to speak because of the varying quality from story to story and how authors will operate their own beta tests. Some might have a cut off point in the public demo but will have the “full length” version for private beta testers (i.e. Wayhaven Book II) while others might not.
It works similar to my expectation to a CoG demo in that, I expect there to be enough content to sink my teeth into. I need to get a good feel of whether or not what the author is “selling” is what I’m looking to “buy”, so to speak.
If a demo is from an author or a part of a series that I love/know, then I’ll probably give the demo more leeway because I can trust the author is going to deliver on what they promised.
For example, if I want to play as a superhero, I’d play Fallen Hero rather than the Heroes Rise trilogy because the former “sells” and “delivers” upon my expectations of what a story about heroes “should” roughly be about.