Ephemeral ports are temporary ports assigned by a machine's IP stack, and are assigned from a designated range of ports for this purpose. When the connection terminates, the ephemeral port is available for reuse, although most IP stacks won't reuse that port number until the entire pool of ephemeral ports have been used. So, if the client program reconnects, it will be assigned a different ephemeral port number for its side of the new connection.
Windows default provide the limition to be 5000 in windows 2003 and 15000 in windows 2003.
Question #1: Will I need always tuned the port range?
Answer #1: Yes and except you know your client will be intranet connections. And each connection is short-around request and response so can finish very quickly. And time_out setting you should also consideration.
10000 client of intranet Server port range is 5000
If each connection can be finished below 500 ms, so you won't need tuned the port range. Otherwise you need.