The adenoids are a single clump of lymphatic tissue in the back wall of the throat (pharynx), between the nose and the mouth, that are create defenses against infection in early infancy. It contains white blood cells of the immune system. In early childhood the adenoids are probably useful in developing immunity against infections; however, later on, it is unlikely that they play any significant role in maintaining health. They usually shrink until they disappear.
Since we generally consider antibody production to be a good thing, many studies have been performed to clarify the importance of the adenoids. There seems to be no adverse effects on the immune status of patients who have had them removed. The adenoids get larger between birth and four years of age; then they become progressively smaller. By adulthood they disappear altogether.
However, suffering from any of the above problems for years may be too high of a price to pay for waiting.  In particular, snoring, and mouth breathing may result in permanent adverse changes in facial or dental development, in addition to the adverse effects on growth and learning caused by failure to thrive and chronic poor sleeping.