Well if you read the Evergreen manual… it is pretty darn close to 24/7.... unless they have changed it.... IMO, should be at least equal time in and out of the crate... of course all situations are different... but that is the rule of thumb I mostly try to go by....
I have the 2002 edition and it states
"If no one is free to supervise the puppy, it is probably best to crate him if he cannot otherwise be restrained from mischief".
It does have a larger piece in the house-training section, but it is mostly about dealing with a young puppy that must be confined for four to six hours a day – if the owner is working,etc.
The trainer I took Jazzy to recommended only letting the pups out of the crate to go out for potty and 10 -1 5 minutes of play time every two hours. It was EXTREME crate training, IMO, and there was no way I was going to do that! UGH>