It most likely has a lot to do with the display tech. I got 8 days out of the PineTime, which was LED (I assume). You couldn't see anything if the display wasn

It most likely has a lot to do with the display tech. I got 8 days out of the PineTime, which was LED (I assume). You couldn't see anything if the display wasn't turned on. I just bought a BangleJS (quite a bit cheaper than the Core 2 Duo, but no speaker and only one button) and the estimated battery life is a month. It uses a colour LCD, making the display visible whenever there is light. For example, daylight makes the display bright. It has a light source that gets turned on by the button. The Core 2 Duo has an e-paper display that only draws power when the display changes.