Battery should not go dead after a week sitting, so something else is going on. That being said, I leave my 03 in sleep mode whenever I put her back in the garage:
Key in ignition, windows up
Cycle key TOWARDS you, and back to off, 4 times
Hit the drivers door lock button up, the car will chirp
You are now in sleep mode, exit car, it will lock. Now, this is where some folks' experiences differ. On MY car, the fob is then disabled, and I have to unlock the car using the keyhole in the door. Some don't have to do this.
I've used sleep mode with car not on a tender for weeks at a time in winter, and it works. Hope this helps
