I like my Steripen Opti. However, typically I use it to just zap one liter of water a day while on the trail. Once in camp, I usually do 3 liters of water in a gravity filter (Sawyer Squeeze). The gravity filter setup gives me enough water for the evening meal and morning meal and lets me start the day's hike with a liter of filtered water on board while conserving the batteries of my Steripen. If I need more water during the day's hike, I break out the Steripen and zap a liter at lunch or rest breaks. The combo approach gives me flexibility and a little bit of backup in case one or the other fails.

Live is good. Eternal life is better!
Richard