For clarity, OPC.three is referring to .NET CommandTimeOut property for the client accessing SQL server. http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.commandtimeout.aspx

SQL server itself has no default timeout for queries running directly from a client, but it can be set manually at the server level via sp_configure 'query wait'

http://msdn.microsoft.com/en-au/library/ms189539%28v=sql.105%29.aspx

There is however a default 10 minute timeout for remote queries against other servers. http://msdn.microsoft.com/en-au/library/ms177457%28v=sql.105%29.aspx