Charles wrote: When would persistence not make sense when trying to accomplish something that's non-trivial?
When on balance the thing you are trying to accomplish isn't actually worth the effort?
That's a reasonable answer. When else?
When you're a child and your idea of presistance is "But I need it" repeated every minute.
There is a point where the results of persistance just sour the whole experience for you; well it did for me anyway.