Quote from Arus;338884:
An average life span isn't truly indicative of the highest age one will reach in his or her lifetime. Also, even many modern medicines can be made from things normally harmful to us, such as animal venom, and any medicine can be considered poison if taken in too strong a dose. And don't forget that this is a fantasy world where injuries can be recovered using potions and magic and alchemy exist, so things probably work very differently.
You don't run around consuming spider poison if a spider poisons you, though. You process it somehow, at the very least. And even then, you still don't consume it.
Also, even with all that magic/potions, remember what happens in Wake Up Call?