What about changes that are required during off-hours when there there is a problem: Wait until works hours to implement in production? Is this not a consideration given the context?
We do code reviews for all committed code, but if there is an emergency in production, we deal with it the best way we can. If that means a quick fix put directly in production, we do it, but there is always a review the following day. Process is great until it isn't working - sometimes you have to side step it or even change it.
But, also, strive for a level of code quality that doesn't require that sort of thing.