Your Wave’s battery life is affected by a wide range of factors including the temperature of your skin and your environment, the types of warming or cooling sessions you use, and how often you warm or cool in a given period. Different types of sessions use different amounts of power.
You can think of your Wave as a runner in a sprint vs. a marathon: it can operate at an intense pace for a short period of time, or it can run for a longer time at a more moderate pace.
For example, shorter sessions at higher temperature levels will use more battery power because your Wave is working harder to deliver more intense sensations at a more rapid pace.
In contrast, longer sessions at lower temperatures place less strain on your Wave and consume battery life more slowly.
You can always keep an eye on your Wave 2 battery level in the top right corner of the app: