Event Hubs Standard tier currently supports a maximum retention period of seven days. Event hubs aren't intended as a permanent data store. Retention periods greater than 24 hours are intended for scenarios in which it's convenient to replay an event stream into the same systems. For example, to train or verify a new machine learning model on existing data. If you need message retention beyond seven days, enabling Event Hubs Capture on your event hub pulls the data from your event hub into the Storage account or Azure Data Lake Service account of your choosing. Enabling Capture incurs a charge based on your purchased throughput units.
You can configure the retention period for the captured data on your storage account. The lifecycle management feature of Azure Storage offers a rich, rule-based policy for general purpose v2 and blob storage accounts. Use the policy to transition your data to the appropriate access tiers or expire at the end of the data's lifecycle. For more information, see Manage the Azure Blob storage lifecycle.