The ExtraSpinUpTimeSecs setting will be stored on a per hypervisor connection and persisting across DDC upgrades in the cloud. 
 
This article serves to document the per-hypervisor location where the ExtraSpinUpTimeSecs setting is stored.  More details here:
 

1. The setting is now stored as part of the hypervisor connection, the customer will be able to update the setting themselves via PowerShell.
2. Azure plugin has been updated to have a higher default as this is the plugin that seems to show the most issues (i.e. slow to start) (240 rather than 120 seconds)

Note: - If the customer has already defined the property in the registry, this will still override the hypervisor connection setting (registry setting takes precedence).  This is relevant for On-premise customer cases where they have already had to define the setting and don’t want to changed just because they have updated to the latest version.  ExtraSpinUpTimeSecs is stored at the below registry location:
 
"HKEY_LOCAL_MACHINE\Software\CitrixDesktopServer\ExtraSpinUpTimeSecs"
 
For more information on Registry keys used by the Broker service, refer to KB article https://support.citrix.com/article/CTX126704
 
Removing the Registry key will cause the hypervisor connection metadata setting to be used.

Caution! Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

When a hypervisor connection is made, there is a new piece of metadata on the hypervisor connection (note the default is the same as the broker setting was 120, but Azure connection where the default will 240), this is consumed by the broker at the time of launch/reconnect (example)
 

 
This setting can be updated by the customer or DevOps using the following PowerShell (in cloud, remote PowerShell will be used). 

Given here is a sample of PowerShell commands used where we update the connection with a new value of 360 seconds:
 

asnp citrix*
get-xdauthentication
Set-HypHypervisorConnectionMetadata -HypervisorConnectionUid f88d5fbf-3dba-4a79-8f86-b94d66e23c30 -Name Citrix_Broker_ExtraSpinUpTime -Value 360

Further, using the PowerShell commands give here, the MetaData field can be fully expanded to verify if the value has been successfully modified.

(get-item XDHyp:\Connections\" <connection name> ").MetaData | fl

Or

Get-Item XDHyp:\Connections\"<connection name>" | Select -ExpandProperty MetaData

The below PowerShell command output confirms if the value has been updated:

Note: Modifying this setting must be done with caution as it affects all VDA connections and reconnections from that point on. (i.e. no waiting or service starts required)