Wireless Sensor Network Lifetime Estimation
Let's take the "Weather mote" that has an average power consumption of $$717·10^{-6}W$$ 

It is powered by a 2.8 V battery and therefore its average current consumption will be $$I=\frac P V=\frac {717·10^{-6} W} {2.8 V}\approx 0.256 mA$$

Because the battery capacity is \$860 mA·h\$ the battery time will be: $$t=\frac {860 mA·h} {0.256 mA}\approx 3358 h=140 days$$

The other estimates can be calculated following the same steps.