Battery discharge in 2025 x3

All,

I was out of the country for 2.5 months and when I got back, the battery was completely discharged. Had to request bmw to send somebody to jump start the car. He mentioned that the battery often gets discharged in a week if the car isn’t used. Hence wanted to listen to the experts here.

How long can the car be unused before the battery completely discharges ?

Thanks