We recommend combining the Wafer with the Field Spray. The Wafer is meant as an enhancement to the field spray. Using just one Wafer will work in light to no-wind conditions, but is not as effective if there is a consistent wind. The Scent Thief Wafer is oil based and evaporates slower than the water based spray, that's why we recommend using the two together.
The Wafers come in a resealable pouch and should last two full days or four hunts. You can recycle a dry Wafer by spraying it down with Scent Thief Field Spray, but the formula used in the original Wafer is a stronger formula, so an original Wafer will be more effective than a recycled one.