How about:

Code:
alias idlemsg {
  if ($idle > 3600) { .timeridlemsg4 0 3600 amsg 3I've been an Idle Chat User for an hour now! 7 Give up saying my name!  5Please leave me a message! :) | halt }
  if ($idle > 2400) { .timeridlemsg3 0 3600 amsg 3I am still an Idle Chat User! 7 Give up saying my name!  5Please leave me a message! :) | halt }
  if ($idle > 1200) { .timeridlemsg2 0 3600 amsg 3I have joined the ranks of being an Idle Chat User! 7 Say my name if you need me. :) | halt }
  if ($idle > 300) { .timeridlemsg1 0 3600 amsg 3I am currently joining the ranks of being an Idle Chat User! 7 Say my name if you need me. :) | halt }
}


This way you dont auto fire off than one even if there's more than one statement that's true

Those who fail history are doomed to repeat it