What's your secret to longevity? Do you not push tempo to, hopefully, lessen the stress on your body?
My secret? Genetics. I used to tell people that would ask about what I know about their injuries: “I don’t really know, I don’t get injured.” That isn’t true anymore, I’ve been nursing plantar fasciitis for about six months now. But I will say this about injuries: if it doesn’t get better in a couple of days, take a little time off, and see a doctor if it persists more than a couple of weeks. And my other “secret” is to be reasonable about your mileage. OP has the right idea with a few runs a week at a reasonable distance. I don’t do that, that’s probably why my foot hurts right now. You can miss a day, none of us are going to the Olympics.
Otherwise, after 40, don’t just run. Do yoga, lift weights, ride a bicycle once in a while. Sacrifice a run if you have to so you can lift twice a week, you’re not getting any stronger. Take ten minutes with a YouTube video to do some yoga, you’re definitely not getting any more flexible. You should do these things when you’re young, but they are almost a requirement after age 50.
Keeping 80% or more of the volume at an easy effort is part of that. I think diet helps, because depending on what you eat, you are could be contributing to more or less inflammation in the body, which both could make injury more likely and recovery slower. I eat whole-food, plant-based.
I expect a good stretching routine would also aid injury prevention, but I've been pretty lousy about that most of the time.
To maintain my fitness, I do a mix of gym strength training, bike riding, and running, which also helps reduce some stress from any one type of training.
Average heart rate is around 140.