I've traveled with the Osprey 50L backpack, and it stood up well to the rigors of long-term travel. This pack is highly praised for its solid construction and comfort, which makes a big difference when you're on the move for months. It’s designed with smart features such as adjustable straps and a hip belt that distributes weight evenly, which is fantastic for both hiking and city exploration.
Regarding size, 50 liters can be ample if you’re disciplined with what you pack. It encourages minimalism, which is a plus because it makes carrying your bag much more manageable. You’ll likely be doing laundry relatively often, which is common practice for travelers on extended trips. However, if you're planning on carrying a lot of camping gear, you might find yourself a bit squeezed for space. In that case, evaluate the necessity of each item and consider if a larger pack would ease your load.
For packing across various climates, layering is your best friend. Opt for moisture-wicking base layers, mid-layers for warmth such as fleeces, and a reliable outer layer like a waterproof jacket. Light, compactable clothing that dries quickly is ideal. Packing cubes are also a lifesaver to keep things organized and allow you to fit more into the space you have.
Have you decided on the kind of gear you'll take for camping? That might influence whether the 50L will suffice.