Re: Clock slowing down
The main battery is not responsible for the slowing clock. Inside your instrument cluster, there should be a small lithium battery to keep an internal clock alive despite the main battery going flat. When you disconnect the main battery, the car will lose most of its settings like seats and mirrors. But the radio should be fine cos the settings are stored in a different kind of memory chip.
As for your key memory, the seat / mirror positions and such are actually stored in the car's body computer. When you press your key, it sends out a code to the car and the body computer compares it to the registered keys and decides on the necessary actions like opening locks, adjusting the seat, mirrors, A/C settings and such.
Registering a battery only keeps track of the battery change dates. There are some experts that claim that the DME lowers its charging cycles for new batteries as they are more receptive to charge cycles. But this fact has not been proven.
So for a slow clock, it seems like the quartz crystal is starting to fail.
Jason, if your clock goes dead after parking for the night, chances are the primary memory fuse to the instrument cluster has gone kaput or there is some faulty wiring. I am guessing that the eooror happens when your car goes into hibernation (about 16mins of no activity when the car is off)