Most of my rides are basically non-stop, although on rides over 1-1.5 hours I may have to go fill a bottle or take a leak. With our son I sometimes gamble on riding while he naps - those days end up broken up into the "nap ride" and the "night ride".

The 3-5+ hour rides are almost always non-stop except to refill bottles (on long rides I usually start with 3 bottles next to the bike or to pee. I experiment with gels, bars, etc while doing those rides so I'm usually eating while I'm riding. I try to do about 200-300 cal per hour on long rides.

Last night I did 1:45 straight. Ate one bar, drank about a bottle of water.

A long time ago a friend of mine, racing pro in Europe, asked me if I thought that doing 2 rides totaling a certain time would equal one ride of that same time (so 2x2.5hr vs 5hr). He wanted to do 2 rides a day because it was easier. That by itself told me that doing one ride would be harder. You're forced to recruit rarely used muscles as your main cycling muscles get fatigued. It's those muscles that make a rider complete, allows a rider to get into a lower, longer position, etc. As you develop those cycling specific muscles you enable your body to get into a more "experienced" riding position. This is what makes a Cat 5 look like they're upright compared to the same rider a few years later when they're a Cat 3 or whatever.