Just weighing in here-
I work from 9-6 every day w/ a 40min commute each way. I put in 90-100 a week and honestly it's not so much whether I'm doing workouts or just running easy that makes 100 difficult, the hardest part is the morning double 2-3 times during the work week. I don't find the number 100 to be too terrifying, I find the mental aspect of choosing to give up an hour of sleep to go running in the cold the most difficult part. If you get used to that, it's pretty simple if you're not a bio-mechanical nightmare when you run and you sleep enough