maybe 10 is a bit more than really needed? After all, this isn't rocket science. You can never be sure if the selected shutter speed is enough, anyway - unless it is really fast (which depends on the lens).
The amount of shake from hands still depends on the time of day, how many cups of coffee or Coke has been consumed, on the body position as well as on what you are standing on and on many other parameters. However, it could give a hint about the results to expect.