Persistence in anything depends on how much it matters to you. Not what the magic winning formula says, sold to you by the next ‘expert’.
It depends on whether you want short-term easy or long-term rewarding, in fact, it depends just on what you want, and what success looks like to you.
Of course, you may reach a point when you have tried and you realise that something isn’t going to work for you. Sure that is the point to change to a different path and allow the journey to evolve in a new direction.
However, it is worth investing time to keep modifying, reimagining, and learning while it still matters to you.
The thing is, there does not have to be a point where something has to have worked by or not.
Things can keep improving if it matters.