Explanation:

Custom Object syncing in Marketing Cloud Account Engagement can take up to 4 hours, as it is not as frequent as Lead or Contact syncs (which occur every 2 minutes). Custom Object data is usually used for reporting, segmentation, or personalizing content, so the sync interval is slower to preserve system performance. Understanding this delay is important for time-sensitive campaigns or automations that rely on this data. If you need immediate use of a custom object field, it’s important to plan accordingly and allow for sync latency.