If you wait until your smoke detector starts beeping before you change
the batteries how do you know that the batteries didn't simply die
really fast one day, and it beeped for nine hours while you were at
work, then stopped?

Or if they beeped themselves dead when you were away for a weekend...

The 'beep when batteries are low' is a nice feature but probably not
one you want to risk your life trusting.

Shaun Eli
www.BrainChampagne.com
Brain Champagne: Clever Comedy for Smart Minds (sm)