I don't think it's that easy to measure or to quantify. For sure aging may play a part as well. At this point, it's too late for me to change the past and all I can do is try to eat well, stay hydrated, get enough sleep and some exercise every day.
No one here can really answer your question, but it's really good that you've quit drinking now. Give it a bit more time. I didn't feel like I had "recovered" completely for nearly a year. I've been sober close to nine years now and I can't really tell how much is some sort of damage, if there even is any, and how much is just general aging. At 40 you should still get a very good recovery, and don't let those youngsters get to you.
No way I'd want to go back to my drinking twenties.