As a somewhat older developer, I find this a surprisingly difficult question to answer honestly. Comparing myself to myself from 10 years ago, I sincerely think I'm more effective, but self-delusion may play a part in that. I've probably lost some of my "step", in terms of raw capacity to memorize and compute mentally, and I have more commitments outside of the world of software, which dilutes my efforts further. Then again, the strategic ideas I have are more dependably correct, and I spend less time chasing down dead ends, either because I've been down them before or had the good luck of witnessing them second- or third-hand.
I've gotten a chance to see a world-class developer very closely between the ages of 36 and 45. He started this period as, very easily, the greatest engineer I'd ever even heard stories of, and I'm pretty sure he got better over that decade. It can be done.