3-5 Years minimum in my club to shodan, and your not considered a sensei until sandan and not really considered a master until well never really, its a life long journey not a race to the next belt. I have trained in Isshinryu for 3 years and am a nikyu hopefully testing for ikkyu in January. I also have several years experience in jiu jitsu and WTF taekwondo, so I have progressed fairly quickly in Isshinryu. Take your time learn all you can, make lasting friendships and most of all have fun! Being a Master is not nearly as much fun as the road to get there.