Edit: That's more like 8 minutes rather than 42 minutes.
Looking at the last 30 blocks on Slush, if you left after 8 minutes, you'd only have hit one block. Certainly not a way to maximise earnings by hopping, so I'm sure Slush won't mind the example

With the hitchhiker, err, "Deep Thought coefficient of pool hoppi-ness", you'd have hit 8 blocks before jumping.
I think you may have inadvertantly proved
science fiction trumps
statistics 
I jest!
I really appreciate the worked example, thanks organofcorti.