Do you mind to expand a bit about no zeros in pace. I am really interested in hearing what people say who do try to do this ride at a brisk pace.
Context: I was a 26-year-old male biking ~2200mi/year of mostly flat suburban riding in the Bay Area. Common daily mileage was usually 0-15mi. Every so often there'd be the spice of a longer day (30, 40, 60, 70, even 100mi), sometimes into the nearby mountains, tackled with no preparation. I'd return hungry and weary and slightly sore but not really worse for wear. Before this trip I did no extra riding, planning to ease myself into it as necessary at the start.
In some ways I don't actually consider my pace that brisk. Distance-wise, sure. (Although, daily distance varied a lot: 24mi the first day from a last-minute snafu, a few 60mi days scattered around, an 80, a few 90s, a bunch from 100-134, one 140, one 161.5. I wasn't consistent for a variety of reasons: shelter spacing, the previous day's distance, random lack of energy, flat tires and maintenance stops, &c.) But I averaged 12-14mi/h a day fairly often. (Max 17.7 in KS with tail winds, min 10.5 from Folsom to Cooks Station early on, uphill.) 15-16 and such were fairly common after I got past Pueblo. I did mileage by doing the time, not pushing the pace. (That longest day was 11.5h riding time.) The longest distance I could sustain day after day was ~125mi (I think my most consistent stretch was three days of four at 120mi/day, across Kansas). Past that I dragged the next day ("only" 90-110mi). I didn't actually catch up to my required overall pace until the last day, although I probably could have pushed and caught up earlier if it'd been necessary.
Health-wise, what I noticed most about averaging 100mi/day was that I always felt on the edge of a cold and cough: slightly out of breath, always a little weary (not in the tired sense) every morning. I got stronger over the trip, but with never a day to heal, the partial exhaustion never went away. Look forward to being constantly weary.
The pace also meant I didn't have much time for sightseeing. I'm mostly pretty happy just going through places and not taking lots of time for stops and attractions -- or just watching the surrounding scenery. My favorite state was Nevada, of all places. (The cycling in Utah was probably better, because you got the vast empty stretches and a bit of scenery both. But I'd rather bike Nevada again than Utah.) Still, there were exceptions, like Monticello (mostly from having read Bryson's At Home the year before, which discussed Monticello a bit and put it in my mind). You're not going to explore much off-route.
Eating also broke down a little due to pace. Early on I ate lunches and often dinners in sit-down diners and the like, because I didn't push as hard on the Western Express. But after Pueblo, more often I ate out of gas stations, sometimes even grabbing food to go for dinner at my ultimate stopping point. Prepackaged sandwiches aren't haute cuisine. But they can work, if you need them to.
All this said: 100mi/day is 7-8h of riding. If you're not taking too many long breaks, you'll have down time. If you're eating in restaurants and not having to put effort into preparing food, that's even more down time. I managed to read a couple thousand pages (on a Kindle) over the trip, even with the pace. You'll be more weary than tired, generally, but as long as you have food and water in you, you can do the mileage. For a good cyclist, the challenge of the pace is mental, not physical.