The correct answer is: never. Never stop. The jazz will never get the talent needed to get any further ahead except for sheer luck in the draft, like with Gobert and Mitchell. And since we are already on the training treadmill we need to stay there until we luck out again or the league agrees to let us get a top 3 pick. I know we aren't the league darlings, like San Antonio and Dallas or the vaunted Lakers, but eventually they might want to cover up the fact that we are the league farm team and give us a shot at a #2 or #3 pick, probably in a ****** draft like the last couple of times we got the #3 picks, but hey, we could get lucky!
So the next answer is never stop tanking until we get that lucky draft that let's us hope we are out of the NBA sewer for a while.