Shared printers lists on NT are broadcast every 10 minutes. If you have a lot of print servers, you may want to extend the broadcast interval.

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Control\Print
Name: ServerThreadTimeout
Type: REG_DWORD
Value: 36000 milliseconds (default)

You could extend the interval to up to 1 hour (3600000).

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