All batteries are not created equal. Just the opposite. Alkaline high discharge batteries like standard Energiser don't last as long as cheaper Heavy Duty batteries, which are designed for more sustained period use. E-batteries, designed for electronics use, are better yet as they are designed for lengthy discharge at relatively small amperage draw.
There's a switch on your motherboard. When you disengage All power, the switch disengages and allows the battery to power the bios chip. If there is any power whatsoever in the pc, meaning if the psu is plugged in and the switch in the On position, the psu is responsible for bios chip. Regardless if Windows is actively On or whether the PC is actively On or not.
There's enough power in a standard CR2032 to maintain a bios uncorrupted for @ 6 months or more. So if your battery is dying in far less time than that, you have a motherboard issue where that switch is not working correctly and it's allowing psu voltage to siphon off the charge/overcharge the battery and killing it.