If you specify a custom retention period for snapshots that you created, you can extend the retention period before the snapshots expire.
If the remaining snapshot retention period of a snapshot is a few days such as three days, Released After {days} Days appears in the Retention Period column corresponding to the snapshot on the Disk Snapshots tab.
Limits
You cannot extend the retention period of snapshots that are permanently retained.
You cannot extend the retention period of snapshots that are shared with you.
You can extend the retention period of existing snapshots but cannot shorten the retention period.
Considerations
Alibaba Cloud charges standard snapshot storage fees in each region based on the snapshot capacity and storage duration. Extending the retention period of snapshots increases snapshot storage costs. For more information, see Snapshots.
If the Delete Automatic Snapshots While Releasing Disk attribute is enabled for a disk, when the disk is manually released or released together with the associated instance, or when the operating system of the associated instance is replaced, the automatic snapshots of the disk are automatically deleted on the disk release even if the automatic snapshot retention period does not end. For more information, see Configure an automatic snapshot policy for a cloud disk.
Procedure
Log on to the ECS console.
In the left-side navigation pane, choose .
In the top navigation bar, select the region and resource group to which the resource belongs.
On the Disk Snapshots tab, find the snapshot that you want to modify and use one of the following methods to extend the retention period:
Choose
> Extend Retention Period in the Actions column. Click the
icon in the Retention Period column. 
Extend the retention period of the snapshot based on your business requirements and click OK.
References
You can call the ModifySnapshotAttribute operation to extend the retention period of snapshots.
To prevent unnecessary snapshot costs, periodically delete snapshots that you no longer require. For information about how to delete a snapshot, see Delete a snapshot.