jzmtl, sorry about the delay get back, I always use the nonchargeable so I do get less dosages, I haven't tried the disposables but I would venture to say you probably would get longer time. They do have a small field solar recharger but it takes so long to recharge the batteries (days) that it would be more beneficial to use a higher watt cell. Mine is 40 watts but I use it for a lot of things. I haven't tried it in extreme cold and when skiing up north it and the batteries stay in my pocket. I have the tablets in cas e the cold affects the use of the batteries but I think the Opti may help out a little. It kills just about everything in the water, do some internet surfing and there is a lot of good feedback in general. There was originally when it first came out many moons ago some issues but a lot of the bugs worked out. I think you will like it, they are at a very good price for the performance it offers.