621.125.  Time and place of hearing. — No hearing provided for in sections 621.015 to 621.198 shall be held less than twenty days after the issuance of notice of said hearing except with the consent of all parties.  Hearings before the administrative hearing commission may be held in any county in the state or in the city of St.  Louis, within the discretion of the hearing commissioner after he has considered the convenience of the parties involved.