Breaking the Rules

Mr A is my first long term relationship. I've been with him longer than any other guy I've ever dated. This is a huge no no. I've been told that I should have more long term relationships so I can know what to do and know that to expect. I don't feel that way. I feel this is the right relationship for me.
Mr A has been in many long term relationships. He's even been married before. Sometimes he forgets that I don't have as much experience as he does. I don't think of as a disadvantage. No two relationships are the same. Mr A is nothing like any other guy I ever dated. I hope I'm not like his exgirlfriends (they are exs for a reason).
Since I have limited experience we grow together. We try to find out what works for us rather than relying on past experience. We talk over the issues rather than assuming things are crumbling like they crumbled in the past.
Honestly, I would meet a guy, date him for a few months, and then he'd disappear, join the witness protection program. I would never hear from them again. I was not worth a reason or an explanation. One guy text messaged me that he couldn't talk to me anymore since we were no longer dating. News to me! Never found out what happened there.
Perhaps none of them were ready for long term relationships. They weren't right for me. I was pushing text message boy. We weren't right for each other.
I used to be scared that Mr A would run away, but that's not his MO. He mets women and trys to build relationships. When we met, we knew that we were going to have a long term relationship. He's the man I was looking for. The man I want to be with for the rest of my life.