I can understand the "At some point, I'm going to stop trying to stay alive for the sake of staying alive" attitude.
I can't understand projecting a fixed age. He doesn't know what his health will be like at 75. If his health starts to rapidly decline at 70 or 65, he may want to change his health-care attitude earlier. If he's still in great shape at 75 he may try to stay alive as long as he's healthy or only suffering acute ailments.
As for me, I'm going to treat my body like an old car: Barring a sudden fatal or mentally-incapacitating calamity, I'll try to keep it running well enough to be "fully functional" until it gets to the point that "it's just not worth it" then I'll cut back on how much effort I spend staying alive. Whether that's 65, 75, 85, or some other age, $DIETY only knows.