[millerhifi]

You should be able to leave sent /received SMS's on your treo with no effect.
Usually what causes the treo to wake randomly is sometimes a 3rd party app will try to do something and will wake the treo like for example if you have "treotools" which will allow you to turn on/off the radio at pre-defined times, this would wake your treo or if you use an email app and set it to send/recieve email at pre-configured intervals. The same would happen if you had an SMS that you typed but had not sent yet, the treo would wake in an attempt to send the pending SMS out.