I used to try and average between 60 and 70 miles per week, I could manage 100 miles physicaly but mentally found it to be a real challenge even more so seeing as I wasn't going to be an Olympic Champion.
  I am presently averaging around the 60 mile mark with one to two hard sessions per week. I still get in some cycling and weight training to keep things interesting and like I have said before "the best training plans are written in pencil " , So I'm not afraid to alter my plans even at the last minute.