Isolated terpenes, cannabis derived or not, do not degrade (or burn) in the same way as a terpene-rich cannabis resin. Those resinous oils and waxes are what protect it from the environment (UV resistance, antioxidants, etc). You can take the terpenes out of the flower but you can’t really “put them back in.”
Using air and letting them “cure” lightly into the flower sort of works, similar to how @Waxplug1 described. It will only absorb so much. If left continuously, the abundance of air exposure will start doing more harm than good. Having experimented with this years ago, it’s only really effective to boost numbers a fraction of a percent. Even so, the perceived benefits of this will be very short lived.
I get people asking about this daily and unless you have capabilities to test for what’s remaining in the final products as well as areas of concern like monoterpene hydroperoxides then you shouldn’t be making anything intended for combustion. When people apply terpenes to flower such as by “spraying” them on is when they’re creating an outright toxic product.
Trying to reintroduce high percentages of terpenes will just ruin the flower as the pure (exposed) terpenes will be susceptible to the surplus of air and start oxidizing, breaking down, etc. Even with low concentrations, the flower will appear as though it aged a year in just a few weeks time as it rapidly discolors to a brownish and eventually beige color. Oxidation of terpenes is a exothermic reaction and will make the saturated material look like it started to burn much like a plant exposed to too much light. Processed in high amounts with excessive amounts of terpenes such as by “spraying,” you are actually creating the ideal conditions to produce and trap enough heat in a pile of flower that it could spontaneously combust.