You did a long run on your own!
For long runs I would suggest that you keep the same amount of time for 4-6 weeks, but increase the pace gradually. Then once you are feeling really strong at the amount of time bring the pace down slightly and increase the time by 10-15 min. You shouldn't go over 90 minutes though. Just go through that cycle starting at 60, building speed, then move up to 75 and go down a little in speed and as you get stronger build the speed up again, and peak at 90 minute runs.
Oh, and probably only one a week, other hard days should be shorter workouts :)
I think I'll have to follow in your footsteps and do a few long runs!