Sennheiser SKM3072 with one 9v batteries.

The graph below shows the comparative battery life of various 9v batteries in a SKM3072 hand held transmitter.

Notice that the Lithium battery lasted almost 26 hours and the alkaline batteries between 9.5 and 11 hours. The Walgreen Supercell test was interupted before it was complete, however the data suggests that it was not performing as well as the other brands.