This morning I was awoken to the lovely sounds of smoke detectors "chirping." Or was it my wife waking me up telling me they were chirping? Either way, it sucks to have to walk around the house to try and figure out which one(s) were going off, but at least it was about 7am instead of the usual 4am. :) Usually the chirping means they are in need of batteries. After we both walked around the house to try and find the offending units, she got the bright idea to proactively replace the batteries. Problem is, we didn't have enough batteries to do it.
We were able to find the offending units (it was more than one of course). The battery in our bedroom was originally installed by the builder, it looks like. Oops!
Oh well, once I go to Costco again, we'll be swimming in 9 volt batteries (and lots of other crap) and I'll go around and finish replacing all the batteries.