I notice that all these vegans seem to be really young. So I am curious, do any vegans survive to old age on this diet?
Kinda. They survive but by and large they are no longer vegans. The longer they live the more likely it is that their "vegan lifestyle" becomes more and more bizarre and detailed until an event gets them properly diagnosed with obsessive-compulsive disorder, which had been masked / expressed via the excessive ritualistic behaviors associated with eating.
The ones that stick to the diet are the ones that never grow up. We sometimes call them liberals.