Albert kept running as long as he had enough stamina left. Even Shella was impressed by Albert's determination.
They didn't have many breaks and when they were on break, Shella protected him to the best of her ability, making sure there were no monsters in the area, especially during the night when Albert slept. She had no need for a break or a sleep anyway, so she could protect him. This was why Yale insisted on Albert bringing Shella with him.
After three days, Albert came to realize that his stamina had increased a little bit from the fact he lasted a bit longer when he ran. His speed also slightly increased.
However, he saw that his EXP or Level didn't have a change, meaning that he could still get stronger without actually leveling up.
He had been relying on his level this whole time to the point he believed the increase of his power solely came from level.
Now that he had proved his doubt, there was one thing he could do.