How many weekly miles should we train?

This is THE question in competitive marathoning. Notice I didn't say "elite" marathoning." For elites it's always well into triple figures during training cycles.

But I believe a healthy runner who wants to race well at the full marathon requires at least 65-75 mpw/average over 16 weeks, with 1-2 faster days and one long day.

But if you are under 35 or so and you can go 80-100mpw, you can't help but race even better.

As we age, it requires a higher injury risk to train to that point. I wouldn't do it. But I'll attempt to average 75mpw with a couple( or three) of 2X days. I want to run my best and ran a 3:12 two years ago 10 pounds over my current weight and running 45 mpw, so now, in the off season, I'm treading 50-55 miles base with some speedwork and will build with the long runs starting February.

To me 70-120 miles is a wide range but an accurate assessment, depending on the runner's history. Runners with natural talent may run well at less, but not their best.