I am saying this as someone with experience. When you find yourself in a relationship with a narcissist, you start by hoping for change. You might even think that with enough patience, things will get better, but what happens in this situation is that waiting for them to become a better person is not just giving them time, you're actually giving up parts of yourself, piece by piece.
The real truth is that a narcissist does not change for love or for anyone. They do not see their actions as a problem so if you're waiting, don't think you will get love back.
Mostly what you get is more emptiness.
Because they don't see themselves as a problem, guess what, you'd never get an apology from them. What the heck is there to be sorry for. I used to think it's lack of knowledge, but as I studied deeper into the subject I realized it's just a lack of care. and that's the hardest part for empaths to accept.
You wait so long, hoping your kindness or your patience will create a miracle, but the only thing changing is how much of yourself you are willing to lose.
I do not believe that love should feel like breaking yourself apart slowly. The moment you notice you are losing your joy and your peace, thats the check engine light of your relationship. Trust me when I say, I have learned this lesson. No relationship is worth the slow death of self-respect.
The only real answer to the question “how long should you wait?” is: stop as soon as you see yourself disappearing.
You do not need to prove how much pain you can take for someone to finally change.