I have a Steripen Journey with the little smiley face display. It takes the guesswork out of knowing if the UV treatment was sufficient. I also called their tech support and inquired specifically about the quiescent current draw from the batteries when the unit is turned off and sitting there with the batteries installed. They told me it draws only a teeny tiny amount of current, on the order of tens of microamps (that's way way less than 1 milliamp). My Steripen was turned off and sitting in the back of my truck for weeks before I used it last time. It worked fine and gave me smiley faces after the required 90 second treatment for both the treatment efficacy and the battery charge status. I would refrain from removing and replacing the lithium batteries every time you use the unit because, unfortunately, I would say the weakest part of the entire device is the battery compartment cover. It is a bit on the flimsy side, and a little tricky to mount properly because there are two very small teeth along one edge that have to be engaged properly inside the battery compartment rim or the cover won't seat properly and be watertight.