In a couple of weeks time I am going for a 6 day hike. I will have no access to power source to recharge batteries. I honestly don't know how long I will have the camera on each day because It will all depend on the weather conditions. With great conditions possibly up to 2-3hrs a day. I plan to do some long exposure shots as well. I currently have 2 OEM batteries but I have not used the OMD enough to know whether this will be enough.