Random11

If you're feeling fatigued, you should take a day off, but you're not necessarily overdoing it. You may just need to build up. Like you, I used to be a runner, and kept at it even though I had increasingly frequent knee injuries and constant knee pain. So I bought a bike about 2 1/2 years ago, gave up running, and have been riding consistently since. My knee pain has gone away (even though x-rays show I have advanced arthritis in my knees). The bike seems to be doing my knees some good.

I'm riding 15-20 miles a day, every day at about a 16mph pace, so by my experience, you can ride that much if you're in shape for it. My bike is a carbon frame gravel bike with 700x38c tires (Specialized Diverge) which is going to be easier to ride than a mountain bike. I'm 70 years old, so I have a few years on you. I'm not sure how much that offsets the advantage my bike gives me.

You can ride that much at your age (or at my age!), so in that sense you're not overdoing it. But if you're fatigued, that is a sign you should take some days off and build up to longer and more frequent rides. Isn't that what you did when you were running?