The fact that the puppy can go 8 hours at night does not mea it can go 8 hours during the daytime. Don't become discouraged. Some puppies will continue to mess in the cage until it is 3-4 months of age. It still would be better for the mess to be in the cage rather than in other parts of the house. Immediately take the puppy outside when it is allowed out of the cage.
Crate training depends upon the instinct of dogs to keep their beds clean.
Their own private place gives them a sense of security. Confinement is not cruel unless abused. The crate should not be so large that he can relieve himself in one end and then sleep in the other, or he will do so. If too large of a crate is used, a divider can be constructed to place in the crate to make it smaller until the puppy grows to the size requiring the entire crate. By making all cage experiences pleasant, the puppy should feel secure and conformable in its cage.