Given that it is the Law that if the Label tells you to do something it must be done. There is some leeway allowed for judgment calls in some cases, and often pesticide labels will purposely be vague or very general to allow this judgment, but let's look at some mandatory statements on rodent bait labels now. First, regarding safety equipment, they state that while handling the bait or dead rodents you are required to wear "waterproof gloves", and that BEFORE removing the gloves they are to be washed. How many folks do that? Then, as soon as is practical you also must wash your hands. Labels also state that you must remove all dead animals, and this may be very difficult to do when the rat or mouse dies in a location where you cannot retrieve it or may not even know where it is. But, at the least you need to perform an inspection of the area to make certain no dead rodents are lying where they are exposed to other animals that may then eat them. 

Rodenticides labeled for use on Norway or Roof Rats and for House Mice now state that they are for use ONLY for those 3 species of rodents, and now cannot be placed further than 50 feet from a structure and for outside use must be placed either within burrows or within a tamper resistant station. Generally you also find instructions telling you to remove any uneaten bait once rodent activity ceases or your service at that account ends. This tells us that there is no such thing as a one-service rodent baiting program. At the least a second trip must be made to remove leftover bait, and this time needs to be built into the cost for that service. 

With respect to your actual question about how long to leave the bait, in the past I would have said this was a "guideline", but with stricter interpretation of rodent bait labels could it be mandatory? Well, most states allow us to follow EPA's guidelines under FIFRA that went into effect way back in the 1980's, where you could use LESS pesticide than the label suggested and at a lower frequency than stated on the Label. In other words, if the Label said "retreat in 2 weeks" you could wait for 3 or 4 weeks and still be legal. Perhaps this statement on the rodenticide label could be taken in this manner, making it okay to remove the pesticide sooner than required by the Label. This would be something that you should discuss with your own local regulatory inspectors, as they will be the ones to say yes or no to this interpretation. 

To me it would only logical in the spirit of using less pesticide and reducing non-target animals to it less to be allowed to remove the bait as soon as you believe it has done what was intended - elimination of the rodents. But, I only take orders too, so getting the opinion of your regulatory folks is always a good idea. I am sure that much of this instruction on the labels is there because of the nature of anticoagulant baits. They are chronic toxins that may need to be ingested over a period of time to take effect. For mice it states to leave the bait for 15 days since they are nibblers. However, we also note an "out" in these statements where they do say to leave the bait for that period of time "or until signs of activity cease", so you would still be well within the label to remove it at any point prior to that 10 or 15 days.