If you have something worthwhile to protect, which is probably the reason why a change review board was established, you do not want add more time to that time window.
No, CABs often get implemented because someone is worried about the damage a borked patch/update could do and doesn't have confidence that it could be reliably fixed quickly. Most of the 'admin' in a change request is things like a process plan (which surely you already know if you're deploying an update to a critical live system) and a rollback process (which again, surely you should be considering before risking fubaring the system).
What I will say is that you should ensure that the CAB members are aware of the need to be able to handle emergency requests (meet, agree and deploy in hours) and should have some process to handle retrospective requests if a business critical update comes out and you can't wait for CAB approval. Normally the requirements for retrospective requests is that it's genuinely critical and that you send a completed request before the update. It might sound odd, but the idea is that they can use that to see if you had properly thought through the process and not just gone Rambo on it.