I got up to a high clip of mileage during my block for Boston this past spring. Not 100 like OP is asking about but 94.5 in 6 days. This was my schedule.
M: Scheduled off day of running, Work from ~8-5, afternoon spent folding laundry, sending out training logs, relaxing.
T: Slept in, Drive to work ~30 minutes, 9-5 work, drive home, 12 mile run at 6:30PM meeting a local run club at 7:00 for some of the middle miles, cook dinner, play some video games with friends
W: 7:00am wakeup, 7:30 am: 5 mile shakeout run, drive to work, work, drive home, 4:30 pm start warmup, 3 mile warmup, 10x 3 minute on/1 minute off @ 5:00 avg, drive to brewery for the run club I host at 6:00pm, 5k @ 6:42 avg, beers with friends, dinner, sleep
TH: AM: 6.4 miles, work, drive to run club starting location, ~5:50ish 12.15 miles w/ middle running with run club at 6:45pm, beer with friends, dinner, sleep
F: AM: 10.65, work from home, went to a brewery opening that afternoon and had a lot of beers.
S: Wake up at 9ish, 11.12 miles w/ buddy that morning, watch f1 qualifying, relax for the early afternoon, 5:40pm: 5.39 miles , sushi and beer
Sun: 7am wakeup, drive to long run meetup, 18 miles w/ 2x2 miles @ hmp in the middle, drive home, probably picked up a burrito, f1 race, nap, clean apartment, dinner
I'm pretty heavily involved in my local running community so I tend to add miles around run clubs to get a lot of my base mileage out of the way. When it's warmer I just wake up to go run around 6am to get the longer runs out of the way. I'm also a 2:23 marathoner that runs his easy runs around 7:15-7:30 so runs don't take too much of my time. I'm running a lot but I try to leave time for being social so that I can have a fairly good balance in life. Work is really important and tends to take priority (as it should) but my schedule is fairly stable so I know when I need to get runs in. If there is something happening throughout the week I'll plan accordingly.
I'm also not married/don't have kids so I have that time to do it. But now at almost 31 I know that high mileage blocks won't be sustainable for too much longer especially as I eventually will settle down and have kids. Running will still be a part of my life then but to a lesser importance. Even now I would say that running isn't the main priority in life as in the grand scheme of things, it's just exercise and I tend to run like crap when I take running way more seriously than it needs to be. As soon as running becomes detrimental to my career or friendships/relationships than I know I'm not in a great place.
Also the comment that says that they don't want to have kids because it will effect their running is probably one of the most wild things I've seen on this site recently.