There was a tread a while ago with someone after advice to help his better half run better. There were suggestions that she wasn’t running enough and need to gradually increase her milage. I tend to time my runs rather than measure them so what is considered a reasonable amount of weekly running time for Oly distance tri’s and Du’s?
My uneducated comment is that it depends on your pace. I’d say you should run a measured course for a set distance (say 5 miles). Do it around a running track if you can to be sure of the distance (4 laps is a mile), and time yourself at a comfortable pace, slower than race pace. Then, you’ll know your average pace/mile, and you can extrapolate how long you’d need to run at that pace to get in your training for various distances. As you get faster, you’ll cover your normal route more quickly, and that’s how you’ll know you’re improving.
I use time as well, but have a pretty good idea of my usual pace so it is easy to convert to miles. I would say you should be averaging around 30 miles a week if you want to run well in Olympic distance races. When I say average 30, you will get the most benefit by doing some run focused weeks near 40 miles, while other weeks may be closer to 20. For me this works out to be around 4 hours per week.