It doesn't break the headtube faster. I don't know why people think that. When you reinforce a deck, it becomes.. well hopefully "unbreakable" That means if it's going to break somewhere, it's going to break.. not on the deck, ergo the headtube breaks.
It doesn't mean it breaks faster or slower, it just means the deck can't break, so after so much use, it will break elsewhere, and seeing as you can't reinforce a headtube, it breaks there.
At least thats what I think. I've reinforced many decks and only broke foldy rails... So I don't know. I just think "breaks faster" is incorrect. But that's just me. It could be right but it doesnt seem to make sense to me