They run down like all battery's, But Cmos Battery only keeps the BIOS clock on Time. When PC is switched off, unless the mains plug is left switched on, this is for desktops. I would not suggest that a Laptop be left with Mains Adapter turned on all the time. Desktop will run of the small amount of power to the motherboard when it switched of but mains plug at wall socket is left in and switched on. The Cmos Battery will then last much longer
This thread is now locked and can not be replied to.