Best way to handle UNC network share time out under Windows 7?

I believe the underlying protocol for UNC shares is Server Message Block (SMB) (SMB2 in Win Vista and later). Take a look at the SESSTIMEOUT registry setting. It sounds related and defaults to 45 seconds,

Microsoft Support - SESSTIMEOUT Information

I'm having trouble reproducing this issue to test modifying this value. Can you add additional information about how to reproduce this problem? How do you make a UNC share unavailable? Remove the system from the network? I've tried an unknown host and an unknown share name, but both requests fail fairly quickly in Windows Explorer.

The timeout is different depending on what version of Windows you are running.

http://blogs.msdn.com/b/openspecification/archive/2013/03/27/smb-2-x-and-smb-3-0-timeouts-in-windows.aspx

Many of the timeouts can be over-ridden via the registry.