One of the biggest differences between a single night backpacking trip and going out for a couple of consecutive days is the need to keep your gear dry. While this is relatively easy in warm, dry weather, it becomes far more challenging if you experience consecutive days of rain or sustained rain coupled with cooler shoulder-season temperatures.
This is when it can pay to carry an extra change of socks, to stop and dry off a wet tent rain fly in the warm sun, or to take a break and make a hot drink with a little extra sugar to stoke your engine and warm you up.
While your body can do an amazing job of staying warm and even help dry your wet clothes while you hike, you need to be extra vigilant when weather conditions, such as cool damp weather or high winds, can prematurely fatigue you or push you into a pre-hypothermic state. Under such conditions, it can make sense to stop, pitch your shelter, crawl into your sleeping bag and take the rest of the day off or until you warm up and recover.
But giving yourself permission to stop and manage the damp can become a problem if you set too aggressive distance goals for yourself and don’t factor in a little bit of extra time or supplies for an unscheduled stop. I suppose it’s ironic that many of us go backpacking to get off a fixed schedule, only to set too high goals that require hiking on one.
For longer trips, it makes sense to hedge your bets and budget in some unscheduled time to handle the increasingly dynamic conditions you might encounter. The only person keeping score of the miles you hike and the time it takes is you.