I experienced quick improvement in my cognition after getting sober (twice) but there can be fluctuations due to physiological factors, stress level, emotional challenges, how satisfied I am with my life, the weather and whatnot. For me the best thing to keep it up is to live a relatively balanced life in a holistic way rather than rely on singular factors. But if there are specific elements that stand out and can be addressed, it is worth a go. I find that restful sleep and a good diet is important and so is doing things I enjoy and find engaging. I also find that a certain level of diversity helps because when my life becomes too homogeneous and repetitive, I tend to become obsessive and grasp onto things too much and that interferes with my concentration. I am also anxiety-prone and that can interfere with attention, realistic view and problem solving ability so it's good to keep an eye on that.