It just dawned on me what it means for a dog to sniff out areas and items for a total of 5 hours a day.
I said 5 hours because that amount of time is on average what a dog is able to handle in a day without losing “sniffing” performance.
To translate this performance in human terms, imagine having to find a needle in a haystack for 5 hours straight – wouldn’t you get blurry-eyed after a while.  Wouldn’t you have to remind yourself mentally and repeatedly what it is you are looking for??
If you still can’t relate to this situation, how about being locked in a small dark room with the directive of having to listen for the sound of a needle falling 8 feet or so away from you on the distant floor.  And keeping scores of how many times you heard it fall in the course of 5 hours.
That is very similar to what my dogs are doing on 5-hours or so day-long assignments.  The good news is that they are dogs and by nature, they love to please you, their master.