I had the best year of my marriage the one after my (former) husband got out of rehab. We went on weekly dates, we talked, he was a different person. Then he relapsed and never came back, even though he did stop drinking right away after the slip.
I am smart enough to know that you can't stay on a treatment high forever, you can't stay on any kind of high for an extended period. But, if the person is working a program, I think what it looks like is:
taking responsibility for one's actions
confessing when a violation has occurred, then apologizing for it
having relationships with clean and sober people
not shutting you out (depending on their personality and how much they share)
I also know that there are bad days and bad periods of time. I know that it's often two steps forward, one back, or even one forward two back sometimes. I need to remember to breathe through those times, even though I am scared of what it might mean.
My experience with a medium-time sober person (2 1/2 years) was that he was still "himself" meaning, had his baggage and ways that held him back, but that he was NOT the same person as when he was using.
Peace....