I’m 72 and can sustain 20-25 mph on my light weight class 3 ebike for a few miles under the right conditions. I get passed by young men and women on road bikes as though I was walking. I stopped worrying about it. Your ability to ride at the speeds you’re attaining is admirable. I hope I’m able to continue at my current level of conditioning here in Northern Virginia where it gets cold and snows, preventing me from riding at all for weeks at a time. (I don’t really mind the cold, but I’m not as adventurous as I was in my youth.)