Yes, it would appear that if you leave a sample out longer it would be easier for the dog to locate, whilst a shorter time would be harder. However, things are not as they appear and it does get more difficult the longer they are cooked as may environmental factors come into play.
Scent will take the path of least resistance.
For example: If it is a hot day the VOC’s will travel with the rising warm air and winds will disperse it over a greater area; whilst cold weather the VOCs hug the land, but still travel with the winds but much lower. If there is high humidity the scent is more ‘visible’ to the dog, whereas low humidity dries out the scent quicker, but the scent could be reactivated with the dampness of evening or dew in the morning.
As VOCs travel the landscape changes and the scent could be caught in many different areas such as small holes in the ground (remember your first video where Tuesday double backed behind the dead tree and lingered? There could have been a pool of scent that had worked its way down from the sample on top of the stump and pooled there), around tree stumps, could be pushed either side of a tree, flow down a hill, or create eddies around the base of a hill. Every obstacle that can be found in the forest, or flat land will give the VOCs an opportunity to be held or travel.
Because of the VOCs taking the path of least resistance, this is why it is so important to ‘get down and dirty’ with your dog. Dogs may indicate in a pool of scent and you need to determine whether to dig the earth or not before you reward them for their efforts. Using an ‘oops’ or similar cue, the dog will learn the difference between the scent and the SOURCE of the scent. And once at the source of the scent, have a BIG party. This secures in their mind what you are after and their body language will tell you what is scent and what is THE source.
With the knowledge that you have of your truffle area, what time of the day would be best for you to search? What are different ways you can test which direction the wind is coming from? What are the advantages of knowing where the wind is coming from? Why would you set your dog to work upwind or downwind?
Look forward to your feedback.