Hi icekeyus. Welcome to the forums.
Do web designers usually create mockups for all of the pages, or do they just create a few before they enter the design stage?
In my experience, just a few pages, to demonstrate any template variations. To do all of the pages would be unnecessary and massive overkill. Often there will only be two or three variations to the basic template, so there's no point repeating the same thing over and over.
These days, some designers don't to a mockup at all but build up the layout in the browser, which is my preference.