tire speed rating void if you get a puncture?

[omodos]

Read this is many places when researching punctures and tire repairs, this makes sense but what are we looking at here? you get a nail in the tread and its repaired correctly or even incorrectly with just a tire plug for example, how careful should one drive if the speed rating has been trashed due to pucnture , for example my X5 has tires rated V both front and back max speed V - 149 mph240 km/h


And I have had a puncture and a repair, would driving at max 120km/h be a no no or is my question like how long is a ball of string?I have never pushed the car further and have no need to, and tires are in very good condition no damage apart from the puncture....