Well I've been getting some longer runs in there. My LT took a few of us he wants to send to Ranger School out on a 6 miler two weeks ago. I almost died because we were at a 6:30 pace the entire time. I couldn't wait for that one to end. Then this last sunday I went on an 8 miler and was able to maintain a 7:30 pace most of the time or 8 MPH. I'm going to try for 9 miles this weekend. Once I reach 10 I'll have to decide how muc higher I want to go. My knee's are still getting used to long distance. They've so used to mid distance it's a little rough on them so I try to take it easy.
Good for you! Getting your endurance up to an hour is really good. I think you'll find you won't have any problems going all the way to two hour runs. After that is what I've always found to be ugly terrritory. It's tough to keep 2-hour plus endurance, but once you've mastered 1-2 hours, you'll be able to crank up to that time and time and time again.
what are you training for?