When I was younger, I always thought I would maintain my weight until I reached middle age. Then my metabolism would slow and I would struggle with gaining weight.
Now that I am in middle age, I realize that this was wrong. I dropped a lot of weight when I lived in Japan, and after that I only gained a steady 4 pounds per year. The problem is that it has been a total of more than 15 years since I came back from Japan. :(