Having seen a car with them flash, is quite laughable.

They flicker on, heat up, then flicker off. Cant be good for the ballast or bulbs.

Why would you even need them for main beam. Come on people, how often do you actually drive with main beam on ?

It starts to get a bit silly; I've seen cars with Bi-Xenon that also have a 'flash' bulb in them, for short flashes, to stop overuse of the ballast used for the main beam. Talk about over-engineering

But it's absolutely right - repeated use of the main beam with shorten the life of the xenon bulb and the ballast. All depends on where you live I suppose and how much you end up using main beam. I found on my xenon-equipped Fabia, an upgraded main beam bulb was more than sufficient.

Steve