Some profesionals have backlogs. Manga artists usually don't but thinking webtoons/tapas both companies usually ask you to have backlogs. Especially webtoons since they need 3 behind paywall.
Manga artists live week by week with a considerable amount of helpers.
Problem is... if the artist gets sick they have to cancel the issue that week. Having a backlog prevents you from falling behind in schedule in case anything happens.
If you want to be effective you need to work limited times a week for limited hours a day with breaks.
Not to mention that your whole project should be planned using a Grantt chart.
This is called project managing.
Many people do the opposite and work most of the time on a tight schedule with almost no breaks.
Some even work 16 hours a day like @darthmongoose mentioned.
It has been proven that doing so is highly inefficient and it will actually take you way longer to finish any type of project/work.
Don't take my word for it you can said studies that prove this by searching.
How do I know all this? I was trained in project management plus I like investigating multiple things.
I find it funny how companies ignore those studies even though their company would be more productive but it has mostly to do with local culture and how they have viewed work for generations. It is hard to break those stigmas.