Nissan: G35 Electrical System Problems

I have a 2003 G35 in which the battery becomes completely discharged when
the car is allowed to sit for more than 36 hours. The dealer has replaced
the battery more than once, but this hasn't solved the problem. I suspect a
short of some sort, but the dealer has not been able to find one.

Has anyone experienced similar problems with the G35?

Any input will be appreciated.

Thanks.