Within a scene where most of it could be done with 3 or 5 shots 1 stop apart imagine there is a really bright source that needs to jump 4 stops. So instead of shooting 9 shots 1 stop apart you could shoot the first 5 then your final shot could be closed by 4 stops. If we are talking an extremely bright light source in an otherwise dimly lit scene there could be some of the light from that bright source falling on objects close to that source and they could use a shot 1 stop open from the most closed. So why screw around? Just take the shots you need from the darkest to the brightest. This may sound confusing, but if you knew about HDR by taking pics for it then you would understand the answer to your question. Once you shoot a successful scene with a very dynamic range you will get it. Personally I cant see taking more than 9 shots, but then maybe I havent come under a condition which needs it. And because what Sparky said is so important to know I will give you the gist of it again......take as many shots or more than you need. They dont cost anything and its better to have too many than not enough.