Speed freak's answer is great but I just want to add one thing: it's not possible to make OHKO moves hit every time.
If you max out your Accuracy it only goes to 3x original accuracy which is 90% for OHKO moves. Pretty good, but not perfect.
Plus by the time you did that 6 times either (a) you'd be KO'd anyway or (b) your attack is so awesome that any other move would almost certainly KO the pokemon anyway. So in my opinion it's a flawed strategy.