An old rule that has been around for ages: The weaker they are, the longer they talk. My other gripe is "breakers" that pop up off frequency. I receive with the synchronous detector 99% of the time, and it takes a second or two for it to lock onto an off-frequency carrier. Usually, by the time the PLL locks onto the carrier, the breaker has already given his call and stood by, so I missed it completely. Except when one is crystal controlled, the is absolutely no reason to break in without first zero-beating your VFO to the carrier of the most recent station that just finished transmitting. If you are crystal controlled, perhaps it would be best to call CQ on your xtal frequency, rather than trying to break into an ongoing QSO that is not on or very close to your crystal frequency.