How far does an average mountain biker ride in any given day?

I'm in the military stationed in Germany. I've recently started taking up mountain biking, mainly on the weekends. Germany is blessed with bike trails in which I use. Usually I log in between 15 to 20 maybe 25 miles in one day. Question is, in relation to someone who goes on a biking like I do (not the touring bike), someone who does it just as a hobby, not a profession do I pretty much ride the same distance as they do?

The non-racers I ride with average about the same as you are currently doing, aside from the two or three yearly epic rides they do, that range from 50 to 100 mi.

Yep 1st answer in on the money. Your rides are normal for an avid biker. If you only ride 1 or twice a week that be lower than the avid MTBer's 3-5 days a week.

You are doing good; 15 mi on a mountain bike is a good workout unless you are pedalling on flat, smoothe dirt paths. Of course it depends on how long it takes you, too. On my usual sunday morning rides, I do 15mi or so in about 2-3 hrs, but I do stop and work on my skills at certain 'fun' spots. One place is a nice steep 10' near-drop that I launch off and then take a short loop back to the top to do it again and again as I work on my form and balance. Another spot is a 100-yd downhill run that has a sandy curve I try to carve perfectly w/o hitting the tree that is right where you want to lean. I have to reverse the route to do that one over and over. One other spot is a hogsback with a 4' drop at one end that is just fun as its kinda curvy and I try to make perfect runs at speed.