added the exact time it takes for migration for this as i worked on this with a customer

we see that the migration where new gateway deployment takes nearly 40 minutes and so this needs to be corrected.

Author: SriramReddyPeddabavi

articles/expressroute/expressroute-howto-gateway-migration-portal.md

@@ -56,7 +56,7 @@ Here are the steps to migrate to a new gateway in Azure portal.
     > [!NOTE]
     > Be aware that your existing Virtual Network gateway will be locked during this process, preventing any creation or modification of connections to this gateway.
 
-1. Select **Prepare** to create the new gateway. This operation could take up to 15 minutes.
+1. Select **Prepare** to create the new gateway. This operation could take up to 45 minutes.
 
 1. After the new gateway is created, you'll proceed to the *Migrate* stage. Here, select the new gateway you created. In this example, it's **myERGateway_migrated**. This transfers the settings from your old gateway to the new one. All network traffic, control plane, and data path connections from your old gateway will transfer without any interruptions. To start this process, select **Migrate Traffic**. This operation could take up to 5 minutes.
 
@@ -68,8 +68,9 @@ Here are the steps to migrate to a new gateway in Azure portal.
 
 
 >[!IMPORTANT]
-> - Before running this step, verify that the new virtual network gateway has a working ExpressRoute connection.
+> - Before running this step, verify that the new virtual network gateway has a working ExpressRoute connection and vaildate if the traffic is flowing through the new connection.
 > - When migrating your gateway, you can expect possible interruption for a maximum of 30 seconds.
+> - Once committed, the connection name cannot be changed and has to be deleted and recreated if one wants to change the connection naming. Please reach out to Azure support in case of any issues.
 
 ## Next steps