delta-9 THC is actually a rather unstable molecule. It can be broken down into non-psychoactive components (cannabidinol, cannabidiol) by exposure to light and heat, but passage of time is also a factor in breaking down THC. Consequently, fresher dope is better dope.
A bud dryer which limits air temp to 29C and which moves a lot of air through the buds removes moisture as fast as possible (around 3 days) without reducing potency. Such machinery also absolutely ensures buds will never go to mould.