If I'm hiking with anyone else, nothing is chambered. If they chamber, I'm not walking with them anymore. There's time to chamber when an animal is spotted.
If I'm walking by myself, it depends. With my BLR I'll chamber one and carefully lower the hammer. If terrain gets sketchy I'll still unload it first. If I'm carrying a bolt action, I'll usually only chamber if I see an animal. If I suspect a predator is in the area, chambered and safety on until I see something.