Hmmmm . . . personally, I'm not too sure on this one.
I'm on my fourth car with Xenons (from 3 different manufacturers), and found you get similar speil from all the dealers re the hotness of the Xenons compared to std Halogens. I think is's a load of tosh, having checked the "hotness" of the lenses, and you can check for yourself.
Simply switch on the headlamps on main beam, so that you have the Xenon dip and the Halogen main - then 15-30 minutes later, check the temperature of the polycarbonate outer cover infront of the dip and the main, and I'll be damned if you can notice any difference!
My suspicions were confirmed twice from two different manufacturers, firstly Vauxhall, secondly Audi. With the Vauxhall, I asked for some beam benders (noooo - I didn't wish to change the sexual orientation of my luminaires!
), and was warned not to use stick-ons, or any kind of adhesive tape - instead, they were gonna sell me - yup, you guessed it, headlamp protectors with built in masks for the offset beam.
The second time, with Audi on my B6 S4, exactly the same question, told not to use any kind of stick-on etc - so I said welllllll - what's the answer?
After much head scratching by parts guy, and some looking on their EPC, they said you CAN use standard headlamp protectors OR Xenon unique beam benders, but not both. I duly ordered some beam benders (well, we can't be upseting our garlic munching x-channel neighbours), and a couple of days later, got a call from Audi garage stating they were now in, but I'd have to book into the workshop and have them properly fitted for another £75 on top of the £50 for the parts (FFS !!!). Having coughed profusely to re-direct a tuna sarnie from widpipe to stomach, I told him I'll pick 'em up and fit 'em myself. Later, having picked them up - ha ha - guess what - the bar$tewards stick onto the polycarbonate outer lens with 3M double-sided self-adhesive foam, right infront of the Xenon bulb.
Myth busted, I'd say!
