The duration of a hypnotic state can vary widely depending on the context in which you're asking and the individual involved. Here's a breakdown:
In a therapeutic context, a typical session with a hypnotherapist can last between 30-90 minutes, although this can vary based on the goals and needs of the client.
Hypnotherapists can give "post-hypnotic" suggestions during a session, instructions intended to affect the client's behaviour after the session ends. The effects of these suggestions can last for varying lengths of time, depending on the individual and the nature of the suggestion. Some suggestions may only last a short time (hours or days), while others can have a more enduring effect, lasting weeks, months, or even longer.
Individuals trained in self-hypnosis can induce a hypnotic state on their own. The duration of this self-induced trance can range from a few minutes to much longer, depending on the individual's experience and intent.
Everyone naturally enters hypnotic-like states daily, such as when daydreaming or getting engrossed in a task (often referred to as 'flow' states). These can last for just a few moments or extend for longer periods.
The lasting impact or changes that result from hypnotherapy can vary. Some people experience immediate and permanent change after just one session, while others may require multiple sessions. Still, others might need occasional "refresher" sessions to maintain the benefits.