How old was the oldest person (a rough estimate) that you have seen slurping on a baby bottle or pacifier?

my Sister, she was 5 and still used a bottle. Well... she has tried to kill me many times (throwing me down the stairs, trying to stab me, kicking me in the head, holding a hot iron inches away from my skin and trying to let it drop) I'd say yes, but no shrink has been able to tell.