I find that a ride will be greatly influenced by how you prepped for it. If I start a ride pedalling out of the saddle hard to sprint even just 100m, that sets me up to ride at a hard pace that challenges my cardio for the rest of the day. I follow that up with some high RPM spinning, some wheelie practice, and other exaggerated movements, like trying to see if I can drag my bars while cornering on asphalt, doing CX running dismounts and mounts, bunny hops, trying to ride on the front wheel, etc. If I didn't eat before, I would only last 1 1/2 hours. If I did eat and brought some food, and water, I'd be able to last 4 hours.
If I just start out a ride pedaling casually, cruising efficiently, that tends to set my pace for the rest of the ride. I find it takes more effort to get out of that groove, to try and maintain a push to go even harder. This pace tends to let me ride for hours on end though, even without fuel.
If I did some push-ups beforehand, the push-ups would seemingly set me up to ride with more weight on the front than normal (more centered in my case) for descents, and be more aggressive with line choice sucking up boulders with the front. If I did some side hops, that would get me in a hopping mood, doing things like hopping double track, hopping if I'm about to lose balance, hopping into a corner with a berm, hopping to escape ruts and braking bumps before a corner, etc.
