Dropping from 130 to 70 miles per week is consistant with my own experience. I base my rides on time, not distance. It's just a lot harder to move fast when I'm cold. I've learned to drop my pace and enjoy the scenary more during the winter months. Besides, winter is the time to develop a foundation, not speed.
Try riding as soon as you can after a snow! Once they've cleared the roads, the miles of white fields are beautiful.