Every time you have your work "checked over by other serious people", it eliminates 90% of the mistakes. So you have it checked over twice so that 99% of mistakes have been eliminated, and so on. But it never gets to 0% mistakes. That's my experience anyway.
I think the expectation is more that serious people have their work checked over by other serious people to catch the obvious mistakes.
Every time you have your work "checked over by other serious people", it eliminates 90% of the mistakes. So you have it checked over twice so that 99% of mistakes have been eliminated, and so on. But it never gets to 0% mistakes. That's my experience anyway.