The scenario is that you have configured a BCS system connecting to a WCF service. Now this service is not connecting to a reliable system and you have a failover node for it. But since BCS by default will keep waiting for the service to respond you will not be able to fail to the other node. You want to change the WCF client (BCS in this case) timeout. To do this it is simple enough but hidden.
You need to change the registry on the SharePoint server. The keys are located under HKEY_CURRENT_USER\Software\Policies\Microsoft\office\14.0\Common\Business Data.
Specifies the number of milliseconds to wait until an open Web service connection is terminated.
Typical values range from 5,000 to 180,000 milliseconds (5 seconds to 3 minutes). The default is no time-out.
To see the complete list of available Business Connectivity Services policy settings, refer to the Office2010GroupPolicyAndOCTSettings_Reference.xls file that is included on the following download page: Office 2010 Administrative Template files (ADM, ADMX, ADML) and Office Customization Tool (http://go.microsoft.com/fwlink/?LinkId=189316).