the cannabis life cycle is limited to a single season. This is how it's always been and always will be—no matter how much we fumble with genetics. Essentially, cannabis grows when the days are long, and flowers when they're short. Once it reaches the end of its life cycle, it dies.
Regeneration is kind of like hacking that biological process. While the original plant will eventually die, growers can first revert it back to its vegetative state. As a result, you can grow the same plant again for a second, slightly less fruitful—harvest.