When fighting the Ender Dragon, the breath became invisible, and sustained itself for over 2 minutes.

After multiple fights and deaths, I can confirm this happens quite a bit of the time. In fact, dying seems to make the invisibility guaranteed, leading to a death when trying to retrieve gear. As I said, it takes approx two minutes to disappear, and is invisible some of the time after the initial attack, and all of the time if said attack kills you.

I should have taken a screen shot but did not at the time, and I do not wish to revive the dragon at the moment.