Fully charging a dead battery takes 3-4 hours.

When a fully charged recorder has been used to make one 16-hour recording, it takes less than an hour to bring it back to a level capable of producing a valid recording. LENA Hub 4.1 and later indicate charge level and time remaining for connected recorders.

The answer depends on the recorder model and its current age.

To be safe, we recommend fully charging the battery no more than 2 weeks before its intended use.

The battery could last 3 years or longer.  Factors include amount of use, charging practices, and the storage environment.

The battery is covered by the recorder warranty.