Look, the only thing you can do is to make sure to use rechargeable batteries and recharge them if you will be viewing 3D for a considerable amount of time. This is always going to be drawback while watching active 3D. But if you plan to go for a passive 3D in the future, you can view 3D on them with plain polarized glasses. Then you can watch 3D for as long as you want without worrying about battery drainage or discharge.