I'm 43 and currently making some of the best gains I've ever made in my life and I started training at 17. I took 7 years off when I was in my late 20's came back in my mid 30's right around when I joined the board. Got in the best shape of my life. Since then I've been inconsistent, taking off at least 6 months every year, drinking nonstop. This year I put down the bottle le, I have my diet perfect and I'm sure that I'll be the biggest and hardest I've ever been. A good 20 more lbs of stage weight.
My older brother is in his 50s and was at his best last time I saw him. He's about 5'6, was always around 165, looked thick and strong as hell at that weight, he's been training since age 14. He got to 190lbs in his early 40s for the first time ever. I know that he takes a lot of human grade GH humatrope. (He lives in Mexico and owns a gym there). I don't think the body starts losing mass until your mid 50s. I should start a thread about that, I have pics from age 17, 19, 35, 37, 39 and present. I'm very confident that I'll look my best and biggest this year.