Puppies/dogs are just like humans when it comes to sleep -- our metabolism shifts into low gear and we don;t have to relieve ourselves unless we have really had a lot to drink or, due to age or illness, our bladders weaken. We normally can go 8 hours without needing the bathroom during sleep therefore... but we'd be hardpressed to last this long all day, even if we have stopped and napped. That's because we eat and drink all day and are active. Dogs and puppies too but especially puppies!
Puppies generally can only hold themselves for an hour for each month of age, plus an hour or so extra, but that is not if actively playing, eating and drinking, when it may be only 90 minutes or so. So a four month puppy should never be left without being taken out for longer than 5 hours and onl;y rarely would a puppy be able to hold itself that length of time anyway -- and this is terribly, terribly long and boring time to be in a crate for a puppy.
Consider that it would be like sticking a young child in a small room for five hours or more and expecting them not to have to go, or to keep themselves entertained. :shock:
Even with adult dogs I never try to leave them longer than 6 hours max without taking them outside -- that's about the comfort limit if they are doing absolutely nothing. A puppy will be up and playing about which stimulates the bladder and bowel. Then they have to go and are trying hard to not dirty their crate -- very tough on a little guy. An xpen is a much better option.
It allows a puppy to move about more naturally and play.
More generally, I really hate crating as a long-term daytime option -- eg putting a dog in for a full day while humansd are at work. That reduces the dog's normal active life down to the period between end of work and bedtime when they are often crated again -- meaning a day is 16-18 hours in a crate for a dog, which would outrage us if zoo animals were kept in such conditions. By the time a dog is about 6-7 months, they can generally do very well in say a full room like a kitchen, made dog/puppy proof. This is a far more comfortable option that a crate with only enough room to stand and turn around or an xpen (which is useful for young puppies). Crating has become a very popular option in some places but I think there really is not enough debate or comparison-thinking on this -- eg that in all other situations for a similarly social and active animal we'd be shocked by such constant confinement to a tiny place. Plus other solutions are so easy -- a room inside.
A crate is a GREAT housetraining tool though and crate training in my mind is a must as it means the dog always can travel safely. And there are many times when it is safer for the dog and useful to be able to have a dog that can be happily crated in the house -- if people are working or a baby is around, for example. Otr if small kids might pester the dog -- then a crate can be a quiet haven.
Also night crating suits many people very well.