How long can blood sit before being centrifuged?

I'm curious to know, how long can blood samples sit before they are centrifuged? Is there a specific time frame that needs to be adhered to in order to ensure accuracy and reliability of the results? Does the duration of time the blood sits before centrifugation impact the quality of the samples in any way? I understand that proper handling and timely processing of blood samples is crucial in various medical and diagnostic procedures, so I'm eager to learn more about the importance of centrifugation timing in this context.