In the al-anon group I went to there were husbands/wives/parents of RAs who had been in each others lives a long time and were happy. I'm not sure what the definition of a "successful" relationship is? but they seemed from the limited information I had to fit that. There were otehrs who still seemed to have relationships that caused them great pain, despite no alcohol being present. I only saw what they chose to share so I have no real idea, and no personal experience of a RA relationship myself.
nothing is certain in any relationship; neither doomed to failure nor set for life. We can only do our best to be the best person we are and trust that whether it works out or not, we will be ok.
Happy christmas!