Your common sense tells you
Don't get me wrong, but if you can add an essay to a topic and necro'ing the topic adds more value to your topic/post then so be it. <-- Implying the post was worth the res with an obvious example.
Don't tell me that ressing a name-guessing topic was worth the res? How do you know this, because your common sense tells you it wasn't worth it.
I know, this can be hard for people so that's why there's a certain leniency with ressed topics, if the crowd doesn't mind, I don't mind (coupled with my own opinion/judgment of the situation), if the crowd goes, "wtfuuck 3 year worthless res you could've just make a new topic" then I'll clean the topic and PM the necroposter, or if the case was more 'severe' + the topic was ressed with what I assume another state of mind, ie; seeking limits/trolling/spamming I will warn you and lock the ressed topic.
Flexibility, that's all I ask of you, it profits you and me, but if you can't be flexible then you're just asking to be judge-fu'd JJJ style.