I've been on Strava since November 2012 and I'm now approach 100k Miles(all real miles, no swift etc). At the start of the year I had approximately 10,200 miles to reach the 100k mark and I gave myself the arbitrary target of doing by my birthday which is the 27th August.
I'm currently on 7,507 miles for the year and my overall total standard at 97,335 miles, so well on target currently. The weather in May was rubbish and I was out sick for 3 days too, so got behind. But June's been good so far and I'm on target for my first 1500 mile month of the year.
The next little mile stone I have after that will be 100k miles fixed as my geared bikes have only done about 4,000 miles currently. (I Should just post that straight in the shit fixie skidder thread)
I don't think strava provides any state around overall miles done by people, but Veloviewer does. There's a guy with over 244,000 miles! and 150 people with over 100k miles. I guess somebody who's in there 20 now might be able to make a million miles.