How do you know when it's time to let go?

I'm really struggling trying to figure out if I should go on or not in my relationship.
There are a few areas in our relationship that have bothered me for a while, I've tried talking about it and we seem to get no where as empty promises are made and nothing really changes. He's a wonderful person and he hasn't done anything on purpose to hurt me, he just lacks effort and compromise and that's what I'm struggling with.
We are a long distance couple and have been for nearly a year. This April I'm moving there so we will be in the same city so I think I've been holding on to the fact that things may be different when we are actually close to one another cause when we see each other now even if it's for two days, it's really good. It's our time apart that ends up causing issues
My question is how did you decide to walk away from someone? Did you follow your instinct? I'm just so lost and confused
Thanks for your help in advance xx