While I can’t specifically answer the GQ, here’s a thread I asked a few years ago on the longevity of seven-footers. Since then, Richard Kiel died just short of his 74th birthday. Kareem Abdul-Jabbar will be 69 next month. Outside of them, and maybe a few others, you’re lucky to get out of your 50s.
I haven’t done a controlled statistical study on it, but men are taller than women, and have shorter lifespans (and are, in particular, more likely to have heart attacks). And there’s a direct relationship between height and the pressure the heart needs to produce, which would provide a plausible mechanism for such a link.
So it may well be that the point at which height starts causing health problems is in the neighborhood of six feet, or even shorter.
While there are different causes of dwarfism, the wikipedia article on dwarfism states that in general they don’t have shorter lifespans.
It’s not just conditions like Acromegaly that cause a shorter lifespan. Just being tall is apparently enough to shorten your lifespan.
In general, being tall is associated with being more healthy. I found several NIH articles that contradicted this (except of course when malnutrition causes a short height), and all of them expressed concern that our attempts to raise taller children, thinking that they are healthier, will actually have the opposite effect.