Reading power consumption data
That is basically correct (the unit of the result is indeed time (hours), that is always a good sign).

But do read the datasheet carefully, the 2000mAh figure is likely to be valid only under the most optimal circumstances.

Note that a battery always has some self-discharge too. IIRC LiPo's are rather good in this aspect, so it might not be a problem.

Voltage gets into the picture only as far as the battery must provide a voltage that is adequate for the device during the entire 2000mAh cycle. That last point is worth checking too.