My AN is about half the size of your husbands, I've known about it for about 3 months now, but I've had had it for 8 years or so based on my first vertigo attack. My hearing changes regularly. My AN ear varies from almost useless on rare occasions to "pretty good" most of the time. I am using my terms to describe the hearing quality as I am too lazy to dig out my tests. I had two tests about two weeks apart and there was a large difference in hearing and speech recognition documented between the two tests that show it isn't just my imagination, these is clearly a large fluctuation in my AN ear's hearing ability.
I asked the Neurotologist why this is and he said it is simply a common condition, but his neurosurgeon partner thought it was more interesting.
I didn't think to ask them your question, how will this effect which type of surgery I choose, until I was on the way home. For now, I am WW so it will be one of the things I ask about in the future, but it's not pressing at the moment.
There is a test that checks the function of the auditory nerve specifically that I haven't had. I think that is the one that tells them what they need to know regarding "how much" hearing you are likely to keep. Others here I am sure have had it and can tell us more about it.
So, the first part of your question is easy,"yes", hearing can vary and change frequently and dramatically. The second part, "I don't know" regarding how that effects your future outcomes and surgery choices.