samba - May 1999 - samba sevices loses login after idle time (overnight)

Would anyone know why IF, my samba 2.0.3 master logon server drops out
after a period of inactivity ?
scenario 1   all client machines off at night , samba server stay's
on, no connections. as client machines
try to logon in the morning they get a message saying "no domain logon
server found", and if they restart
samba  -   #  /root/samba restart
they can login with no problem.?
i have the
null passwords = ok  to avoid any password problems, this system is
kinda a non-security system.
is there a setting in samba to avoid TIME-OUT if there are no active
connections ...Thanks   Rob F.