Just another thought or two. When I began paddling early last year I was immediately struck by the similiarity between paddling and bicycling. Each requires a steady cadence and the most efficient way to use your energy in each sport is at a cadence that matches your physical ability, stamina and environment. For example, when bicycling, I find my body performs best at a cadence of about 85-90 rpms. so I select my gears accordingly. I haven't quite determined my cadence for paddling.
If I were to do a long kayak trip, I'd take two paddles. Not just to have a spare but to have an extra "gear". One wider bladed paddle for those conditions where a high gear makes sense, down wind, calm conditions, conditions where quick acceleration and control are required as in a narrow or crowded waterway. The second paddle would have a narrower blade, less wear and tear on the body, higher paddling cadence, way more efficient over long distance, less fatiguing. Possibly more control in rough conditions 'cause your physically able to place the paddle more frequently with less surface area presented to the wind.