You should only 'gamble' with a positive expectation in the long...

You should only 'gamble' with a positive expectation in the long term. Just like the casinos do.

Yes, I know about the Tasmanians with their off roulette wheel changing the odds but such is very rare now if it happens at all with ongoing monitpring as a matter of course.

I won't repeat my earlier comments on ratios but such are an example of a positive expectation. The odds can change over time - for the better or the worse.