SMB connections are designed to close after being dormant for a specific amount of time (10 minutes by default). Tinkering with SMB connection timeouts can reduce your network traffic, but not in the way that you might think.
As with some of the other concepts that I’ve been discussing, tinkering with the SMB connection timeout values is a trade off. Low connection timeout values cause connections to close very quickly. However, closing a connection quickly may cause a significant amount of SMB overhead because each time you close a connection, a new connection is established automatically
If you are using an ISDN connection or some other pay-by-the-frame or -packet medium, then Microsoft recommends changing the SMB timeout time from 600 seconds (10 minutes) to ten seconds. If you aren’t using an ISDN or similar connection, then you’re probably better off leaving this setting alone because lowering the value tends to increase the amount of SMB overhead.
You can modify the SMB connection timeout value by opening the Registry Editor and navigating to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\parameters. The specific key that you’re looking for in this location is the KeepConn key. This key is a REG_DWORD and contains an integer ranging from 1 to 65535. This number indicates the number of seconds that a connection will remain idle before timing out. For this change to work, you must modify this registry key on all Windows NT servers and workstations.
from: http://articles.techrepublic.com.com/5100-6350_11-5031564.html