Hi mentallyexh,
The other day I was thinking about my exA and turned on the radio. The song that was playing was, "You make me promises, promises...you know you'll never keep...why do I believe?" That was me. There were plenty of "good behavior" stints by my ex, all designed to keep me playing my role as a good codie, which was a role I was really afraid to stop playing.
No one can know how long your A will behave this way. Add that to the list of the things we can't control...
In my experience it wasn't how long "good, decent, human behavior" lasted that I remember most clearly. What I remember is how deep the despair and disappointment sent me "into the abyss" of my own emotions when the other ("bad") behaviors emerged again. And they always emerged again.
Hugs,
posie