Is it possible that I (or
> should I say, my passenger) still may have shortened the battery's life by
> having the dome light continuously on for 9 hours without the car running?
> Or is the dome light less taxing on the battery than, say, the headlights
> and it will be OK?
>
> The battery is an almost 4-year old Sears DieHard, if that matters.
>
> Thanks in advance for any answers you can provide.

No. The drain is minimal. It would eventually kill the battery,
especially if it isn't in good shape. (This sometimes drive people
crazy until they realize that the bulb in the trunk is on all the time
due to a faulty switch.)

If the car still started, I'd say you proved that the battery is still
healthy.

Several years ago, my daughter left the car headlights on until the
battery was cold, stone, dead. I was sure that the battery (a
semi-cheapie Champion) was screwed. But, after a jump start the
battery lasted fine for another 3 years until the car was traded in.

Further proof: I walk my dog late at night. I frequently see
people's car interiors lit up by the dome light. Obviously they're on
all night but the next morning the car is gone....

JM