You can change how often a browser client announces itself. In the registry path, under:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters
add the Announce parameter with a type of REG_DWORD, and set the number of seconds that the browser should wait between announcements. For example, if the default for Announce is 12 minutes, the length of time is set to 720.
The Announce value must be changed on all computers in the workgroup or domain before the new value can be used by all computers. As you decrease this value, announcement traffic increases. Increasing the Announce value reduces the amount of announcement traffic, but will increase the length of time that a shutdown computer will appear on the browse list.