That totally depends on the severity of your pain and whether you are able and willing to commit to some lifestyle changes and do the exercises shown in the article on a daily basis. As a rule of thumb, as soon as you start gently moving and re-aligning the neck, improvement should begin within a couple of weeks. If you stop, the pain may return. Don't forget to stay mobile in the neck with the famous "YES," "NO," and "MAYBE" exercise. Always keep your shoulders loose and relaxed by the side of your body and your head on top, not in front of the body.
Here is another article with a couple of videos you can follow to help you loosen the neck and shoulders to ease the pain.