When do I kill the zone and put it in a black list?

[Ahmedosama]

Hello folks! I'm so confused about how I can exclude the zone and add it to the blacklist especially in push campaigns? I have heard many opinions, like exclude the zone when it reaches the same value of the offer payout without any conversions, and another opinion when the zone reaches half the offer payout without any conversions!! So I want some advice on this