In the 1970s-early '80s I rode about 400-500 miles a month, mostly commuting and some longer weekend and group rides in Southern California. Ideal cycling climate. Then I returned to Texas and stopped riding until 2015.
I didn't record my 2015 rides. I was in such bad shape I rarely rode more than 3 miles at a time the first month. I'd guesstimate I rode maybe 300 miles in 2015.
In 2016 I began using Cyclemeter but didn't upload to Strava. Rode about 1,600 miles.
In 2017 I was just shy of 5,000 miles. Getting a road bike last summer -- my first in 30+ years -- motivated me to ride farther and more often.
My mileage is way down so far in 2018, partly due to a month-long bout with flu and other ailments, and misc life stuff. Maybe 200 miles a month so far. It'll pick up as the weather improves and my stamina returns.