It is what it is. If more goes out (closed-circuit current consumption of 10 - 40 mA) than in you are going to run out of juice. The alternative design might be to not have sleep mode for all the computers and have it shut down like Windows, then you can wait 10 minutes before your car can boot and drive off, that's if you don't get the blue screen of death.
From BMW service.
Long immobilization period
The vehicle was parked for a very long period. The vehicle has a standard closed-circuit current consumption of 10 - 40 mA, depending on the equipment fitted. This leads to slow but continuous battery discharge. Depending on the state of charge of the battery when the vehicle is parked, the residual capacity necessary to start the vehicle is reached after an immobilization period of approx. 4 - 12 weeks. If possible, point out these facts to the customer.
This is not me, my car is a daily driver .
Unfavorable driving profile
The battery can be depleted due to unfavorable driving characteristics of the customer:
- In the case of extreme short-distance driving, it is possible that starting the engine takes more energy from the battery than is charged in the subsequent trip. The charge balance deteriorates if a great many current consumers are switched on during the subsequent trip.
- Very few trips: If the vehicle is moved very infrequently and the individual trips are not sufficiently long, it is possible that during the immobilization period more energy is taken from the battery by normal closed-circuit current than is charged while the vehicle is being driven.
If possible, point out these facts to the customer.