I always have zero days.
For multiple reasons.
I love bicycle touring, but if I simply ride and ride and ride -
then I don't think it's all that different than driving nonstop from L.A. to NYC.
I almost always hike the backcountry in national parks -
from the Grand Canyon to Yosemite to Glacier to Denali.
I've crossed the Grand Canyon six times - you can shuttle your bike around.
I've hiked up from Yosemite Valley to Tuolumne Meadows - the concessionaire took my bike.
I also stop for church and don't want to be too stinky, so I clean up a bit.
I play piano/organ and have played in small churches across the country.
Not only is it a great way to meet people, but there is often good food afterwards - and lots of it.
And there's some story about resting on the seventh day - - I think.
I'm a big believer in sitting out awful weather. Why make yourself miserable?
I'm not talking about a little rain or a headwind or a hot day.
I'm talking about pouring rain, 35 mph winds, or a 100+ heat wave.
Plus, there's a higher risk of an accident in bad conditions.
Not only are you bonking, but drivers may be, as well.
Most importantly, building in off days lets you enjoy the other days.
There are always things that come up unexpectedly.
Weather, breakdowns, food/water that doesn't agree.
If there's no built-in leeway, then you are playing catch-up.
YMMV - Jama
Pic - Heading down to Phantom Ranch on the North Kaibab Trail
If you start down in the late afternoon, camp at Cottonwood,
then continue just after dawn, reaching Box Canyon as the sun comes up,
you can do the entire hike in the shade.