How often do you have to win before it's no longer gambling?

Exactly. It's not gambling if you win most of the time. This is like saying driving a car is gambling. I mean sure, I guess if you think any amount of risk equals gambling.

I don't know where I'd draw the line personally, but wherever you draw it there's a problem. If you give increasingly more advanced tasks to it, you will eventually cross the line.

How is this any different from assigning increasingly more advanced tasks to an employee?

we're winning so much we started complaining "I can't handle so much winning"

Suffering from Success - Studio album by DJ Khaled ‧ 2013

Applies here? :D