Last time this happened to Arthur, he was stuck inside for 7 years. It is a long time for him although he only watched from inside bear's body. It may not be as long as literally living 7 years but it's still a long time, moreover, most of the time it's fighting and the pain is unbearable.
When the darkness disappeared and Arthur was able to open his eyes again, the first thing he saw was an endless sea of clouds. It did take him a couple of seconds to know inside what creature he was stuck currently.
From the two wide wings and long beak, Arthur was sure he was inside an eagle and a big one at that. The process was just like the previous except the lack of battles. The eagle would rarely fight and would only join in to steal a prey or to finish a wounded creature. With its powerful beak and sharp claws, it did quite the damage but the most outstanding thing about it its eyes and speed.