Depends on what you’re playing, for plinko change about every 2000 nonce regardless of what you hit. If it’s dead it’ll be dead for several more 1000’s nonce and if it’s good it will die out.
Best way is to rotate through rows 9-15 and watch how the balls bounce. When they bounce down the middle then go towards the outside (instead of bouncing towards outside first then back in) it’s a good sign of a good hit coming up.