“How long does it take to realign your back?”

Usually couple of sessions to a few. But to maintain it, your doctor may require a treatment plan based upon your history and type of physical work.

How long it takes to realign your spine depends on many factors. How long has it been out of alignment, what caused the misalignment, what part of the spine is out of alignment and to what degree. Other factors include the patients activity, genetic disposition, age, associated condition, and overall health.
It takes less than a tenth of a second to adjust the vertebrae but all the other factors make it impossible to answer the question.

Realigning spine depends on the postural curvature and degree of degeneration of the joints