I saw this in FAQ and said it will decrease the life of the bulb.

But has anyone actually did that?? Given that D2R is fairly cheap and if it did last for reasonable hour, this method should be better than fabricating a metal shield?

You would have to deal with very high temp preburning. Find out how hot glass gets, then add a 100C. Not sure what u would end up on, but probably more than a home oven can do.