I've always found that the water gets low over time, and I simply had overlooked checking this battery.
I've always assumed that since some of the car electronics are always on, there is always a low-current drain on the battery, and lead-acid batteries don't like this. Additionally, we have a Nokia cell phone car install kit in the car, and up until about a year ago my wife would often leave the phone in the car, and it would be charged with the car battery. Throw in a couple of jump starts for my old BMW and I'm assuming that did the trick.
I'll check the voltage across the battery just to be sure.
Originally posted by PaulC
Glad you're back on the road, but why was the battery low on water? Often this is a sign that the voltage regulator is not working to spec and allowing too high a voltage to boil away the electrolyte.