When deciding on a pack for those longer trips, a hike must consider three factors in this order of importance: comfort, size, and features. Longer trips obviously require more gear such as food, camp supplies, and possibly clothing. The season also dictates how much gear is needed almost as much as the duration of the trek. Those venturing out in subfreezing temperatures will need far more gear and a larger backpack than someone who is taking a trip through the tropics.
If the pack is sufficiently large for that long trek but isn’t comfortable, it’s going to be a very difficult journey. Larger heavier packs tend to amplify the ill effects of a bad fitting back. All that weight presses into the hiker more; it can be ignored somewhat with lighter loads. Therefore, it’s important to fully test a backpack before purchase with it packed similarly to your planned pack weight. Borrowing a friend’s pack for testing is a good option. Try to simulate the exact weight and dimensions you plan for on the trail to get a good sense of whether the pack will be comfortable.
The support system influences comfort and wearability to a large degree. Dual aluminum stays are common support structures, but they get uncomfortable and don’t conform to the back well. Osprey packs have eliminated this setup in favor of a peripheral frame system than better conforms to the hiker’s back. This type is generally more comfortable over long hikes.
For hikes longer than one week, the minimum pack volume is around eighty liters as a general rule. It’s true than smaller packs can be used by experienced hikers who know how to pack light. However, for most, eighty liters is standard. This size will provide enough room for food, camp gear, perishables, and insulation.
Depending on whether the trip is in the winter the hiker may need even more space. Many people use goose down clothes and down sleeping bags which pack down really small. They are expensive, but they will allow you to survive in extremely cold climates with very little bulk to your gear bag or backpack.
Larger backpacks offer even more space, but there is an upper limit as well as a lower limit. One hundred and ten liters is about the largest sized pack anyone should buy. A pack larger than this will be itself so heavy that it will contribute to the hiker’s load. The weight of the pack will become a burden.
The standard features found on most hiking packs include: top loading main compartment, sleeping bag compartment, and several side pockets for things like snacks on the trail. All these features are needed for long treks. A convenience feature often added to new packs is a front access zipper. This allows the hiker to get to his or her gear from the middle of the pack without having to dig down through everything from the top. It’s very convenient when you need one thing that you just happened to pack first, so it’s at the very bottom of the pack.
Sleeping bag compartments vary in size, and they are often too small for synthetic bags. However, almost any goose down sleeping bag will fit into them. Smaller summer synthetic one will also fit.