In 156, Antoninus turned 70. He found it difficult to keep himself upright without stays. He started nibbling on dry bread to give him the strength to stay awake through his morning receptions. As Antoninus aged, Marcus would take on more administrative duties, more still when he became the praetorian prefect (an office that was as much secretarial as military) when Marcus Gavius Maximus died in 156 or 157. In 160, Marcus and Lucius were designated joint consuls for the following year. Antoninus may have already been ill.