It's not a common issue and as you've said, you haven't had to run for long periods at slow speed in traffic. It was a problem that afflicted a few owners in the hottest parts of the USA (yeah, I know Florida isn't exactly cool in summer ... ) over the years, that's all. It tends to show up more when trying to restart soon after stopping the motor in high temps, fast evaporating fuel in the carbs causing vapor locks.