<human>: Condense the text into a few key points

I've been dating Dave for about a year in September. A good portion of that time has been long distance, with me living away from him. I just really can't take it anymore...whenever we make plans to do anything, if we state a time, then he is always late. Always. 

The first few times, I tried to be cool about it, because I am late sometimes, too. But it's just a constant thing with him. We have gotten in fights about it a lot, and I have told him that I find him disrespecting me and my time, and he always apologizes and says that he will try to do better. But we just end up in the same situation over and over again. A few months into the relationship, I found out that he had/has ADHD. I did some Googling, and found that people who have that often lose track of time. 

I immediately felt bad for fighting with him, but then it came down to, do I tell him how I really feel, or do I try to deal with this because I know it won't change?

Over the past few months it's really just come to a head where he says he will text, call or do something at a certain time but doesn't show up. It'll be 10 minutes, 30 minutes, sometimes almost an hour past the time he says he will be there. And he never texts to say he'll be running late, or that he needs to reschedule. If he doesn't text for a long time after he says he will and I get mad, he always has an excuse.

Reddit, I need your help. I'm on the verge of breaking things off with him, because he isn't reliable for anything. (I don't feel comfortable talking to him about his ADHD possibly making things difficult, because I'm afraid that he will think I am calling him inept or not mature enough.) He says if we stay together, he will make a real effort to trying to work on the lateness. But I've heard that too many times to believe him. Do people change? Can they change?
<bot>: I'm afraid of staying together with and making excuses for someone who, while a gentle and undemanding person, is not a reliable person. What should I do/what advice would you give me?