Some new research was published about ideal "decarb" times and temperatures for both THC and CBD. Decarb(oxylation) is what makes the acidic forms, THC-A and CBD-A made by the plant, turn into the "neutral" forms of Delta-9 THC and CBD. Cured cannabis or hemp flower contain mostly THC-A and CBD-A, and they get decarbed when smoked or vaporized (heated).
This post talks about the paper (published in Industrial & Engineering Chemistry Research) and the surprising results: THC-A decarbs really FAST and CBD-A decarbs really SLOW....for the most efficient conversion rate. The most efficient CBD decarb takes place at just 176F for 25 HOURS! But the most efficient decarb for THC was at 320F for only 7 MINUTES. Using a little higher temperature (194F) for 12 hours can expedite the process for CBD with only a small drop in efficiency.
But, other research has shown CBD decarb times of 15 minutes at 293F will yield about 76% efficiency. It is NOT the most efficient time and temperature, but for the home enthusiast, it's still WAY cheaper than buying retail.