prespawned listeners

I have increased the prespawn number in the listener on an Oracle instance to 5 and set the maximum to 5 . I notice that that at max there are 5 listener processes running . But I notice no significant difference in connection time from a PC. In fact I have noticed that there are more connect problems with the increased processes .

What does PRESPAWNING listener processes buy me ??

                                      Ja Uhm