You are right, relapse is common, and then there is a slip vs a relapse vs a spectacular relapse.
My hubby did IOP and was sober about 15-18 months-no AA, but did weekly aftercare for about 15 months. Then he began to sneak a few times here and there-drink when I was out of town, etc. Funny thing-he felt guilty going to aftercare when he was sneaking drinks, so he quit aftercare. Nice. After about 6 months of a little sneaking here or there he went of the rails-1drink after work, then 2, then 6...I caught him, he came clean, and then did 30 days IP-the 5 months since he's doing individual, marital, and group counseling, plus AA 5-6x/week.
It works if they work it. I have told him I can handle a slip, but the going underground, sneaking, lying, betrayal...not sure I can handle that again, and he is very clear my boundary is I will not live with an active alcoholic. I don't even know if I would live with him if he stopped going to AAA/treatment with some regularity.
But, you don't need to make any of those choices today. Unfortunately, sometimes quitting does take practice, and the pressure of "even one slip up and you are out" feels like a hard way to live, to me...You will figure it out. Make the most of this time apart by taking care of you.