Updating MacOS can take anywhere from 15-20 minutes to several hours, depending on factors like update size and internet speed.Factors affecting MacOS update duration include the size of the update, internet speed, and system performance.Slow internet connection can significantly delay the downloading and installation of MacOS updates.Older Macs, limited free storage, and slower drives can also contribute to longer update times.Newer versions of MacOS provide time estimates for installing updates in System Settings under Software Update.Progress bar indicators during updates may give a 'time remaining' estimate, but actual times may vary.To speed up MacOS updates, a faster internet connection is crucial, as the update process itself cannot be accelerated.If a MacOS update is taking multiple hours, it's best to let the process complete to avoid potential system issues or data loss.Interrupting a system update before completion can lead to MacOS instability and may require reinstallation.Patience is key during MacOS updates, especially for older Macs, where lengthy update processes are more common.