It took me slightly under two years to flower this species.  I believe that the single biggest factor in success with this complex of Hoyas is to provide enough 12 hour days.  I have had tremendous luck flowering H. macgillivrayi and archboldiana using grow lights to maintain 12 hour day length.  It needs to be in a well draining mix and allowed to dry slightly during the winter months as soon as it starts to produce peduncles and bud up, water liberally and don’t allow to go dry.