The prostate produces fluid that becomes part of ejaculate or semen. The prostate is not a reservoir of fluid but rather produces it at the time of desire and ejaculation. Prostate massagers are most commonly used for pleasure use. I can find no studies that support prostate massage by itself as a way to keep the prostate healthy. However there has recently been a study that correlated 21 or more ejaculations per month with a reduction in the risk of prostate problems. You can read more about this and other suggestions for prostate health here: www.thealternativedaily.com/frequent-ejaculations-help-prevent-prostate-cancer