From the kit page;
The circuit runs on 2 AA cells, and has an external battery box with
integrated power switch. Under high-brightness mode: A new set of
alkaline AA cells would be expected to last about 60-80 hours
continuously, or 10-13 days if run 6 hours per day. Under low-power
mode– the default at turn on– a new set of alkaline AA cells would be
expected to last somewhere in the neighborhood of 400-700 hours, or
16-30 days if run continuously.
10 to 13 days if run continuosly 6 hours per day or in other words 5 to 6.5 days at 12 hrs per day.
Bring one set of spare batteries anyway. (Better safe than sorry!)