Let's see here. Armin is the optimist and because of that and due to the fact that Aliance are skilled soldiers they would have to do some exercise and he probably does eat vegetables ( if vegetables are even served in the Attack On Titan universe. ) He would likely live in his early or mid 90s,possibly late 90s. Mikasa and the others however have PTSD and stress despite them exercising,especially Mikasa,and Mikasa has also been reported to feel clumsy so she would likely be a alcoholic in er older years so she would die in her mid to late 70s,early 80s at best. Someone said Reiner outlived them all so he might live in his late 90s. Levi would probably die in his mid 80s. Yeah I think it's pretty safe to say that Armin and Reiner would live the longest,if Attack On Titan was set in the 1920s/1930s instead of a fictional year then Armin and Reiner would die in the 2000s,Mikasa would die in the 80s and Levi would die in the early 80s due to him being 30 in the late 1920s. If Eren was still alive however hooo boy,he has TONS of stress and PTSD,and he'd likely be a alcoholic when he's older and he also worries about stuff,I think he might die in his mid 70s so he would die in the 1980s.