In my case, I check every (comic) episode at least twice at different stages of completion, once while focused and once when my brain's turned into mush
Most times I'm focused and free from my creator's mindset to spot plot holes, pacing and major issues are when I'm incredibly bored for a short time but can't zone out for too long. Like on a bumpy bus ride, useless draggy work meetings (it rarely gets to that point though) or having to stay too long in the toilet. Proofreading at this stage may result in major changes, so I mostly do this after worldbuilding, sketching & completing panel/page layout.
For detailed spot checks, once the work's (mostly) completed, I'll wait until I'm super tired to check it mindlessly (i.e. without comprehending the story) based on a checklist of my team's bad habits, like typos, missing watermark, unclean line art, facial features, coloring etc.
Of course there're many checks in between those 2 stages and buffer time between checks whenever possible to ensure I have fresh eyes.