At the age of 37 I completely re-vamped my game plan and after being stuck in one place for years I put on 25 pounds in one year and kept the same bf.
A few years later I messed with gear, gained 20 pounds and within 6 months of being natural I lost every ounce of it. Then I did three, 3 week cycles (over the course of a year) and gained 5 pounds each time and kept it all. That made a gain of 15 pounds in one year after maxing out naturally.
All in all, a gain of 40 pounds of muscle while in my 40's.
I did a couple of other short cycles and continued making 5 pound gains but I found I didn't like the way I looked or felt once I got too far beyond the 200 pound mark, so I got myself down to a comfortable 190 with 10% bf. And that's where I am today at age 49.
I could get down to maybe 8% bf, but fuck it. I like food.