Last year I figured out a "climbing course" that basically circles my neighborhood. It's about 3.5 miles long, and gets me about 100 feet of elevation gain per mile. I can ride that in the dark, and in very, very cold conditions and can easily bail out if I want. I do that for an hour or so. I realized no matter how boring that little loop is, it beats spending the same amount of time on the trainer by a mile.