My dogs sleep when they can. If we were to go for a mountain climb (we've done this) then they will stay awake the whole day enjoying nature. But if I am on the computer all day, and they are stuck inside, then they will sleep all day long.
I will say that my doberman/rottweiler and miniature pinscher sleep much more than my schnauzer. But he is about 6 years younger than one and 12 years younger than the other. He would rather be up then sleep. So I think age has a lot to do with it.
In kennels that I worked at I observed that labs tended to have more energy than other breeds - even when they had to stay in their pens...so it can definitely be a breed thing as well.