Anyone found that perfect multiplier number to stop farming?

How much is enough, is a unique value to each person and city. You may be content to slow or wish to go fast; it's a choice.

Increasing multiplier was a pleasurable goal in and of itself, so farming was a means to meet that end. Frankly, farming is a PITA imho so I'd rather have a large multiplier and work very little to achieve my goals; I've stopped at 4000ish% for the moment. I also believe that the status quo won't hold forever so better off meeting my goals in the near term in case something changes.