See post title.
I’m away on a trip with work and a colleague has just let me know that he parked next to my car and the vanity mirror light on the sun visor was on. I’ve been away since Monday evening and I get back home tomorrow at about 5:00 am. Can I expect the battery to still be ok?
My wife manages to get her light turned on all the time in her car. It’s only on for 12 to 15 hours, but there’s no problem starting the car. I’m guessing you’re okay.
that bulb draws little. if you have a good battery then my guess is you’ll be fine.
If the battery is dead then you should only need a jump. Unless the battery is old enough then this might be its final charge, in that case you needed a new one anyway though.
While it’s true that a few hours draw of a little bitty bulb by itself shouldn’t damage the car’s ability to start the next time you try, if you don’t drive (operate the alternator and recharge the battery) long enough to replace the charge lost to the light bulb plus the engine start, the battery will effectively lose charge over time.
This is often a problem with an older battery and an older or less efficient alternator, coupled with lots of engine turn-off and starts with very short run periods between.
It’s not a huge consideration, although I have had a car with that exact combination of circumstances in which removing the overnight power drain made the difference.
YMMV.
The battery should be pretty good, the car only has 10,000 km on it. I’ve sourced a set of jumper cables so if there are any problems I can sort them out. Fingers crossed for the morning.
I wouldn’t be surprised if you do need a jump when you get back. I’m not sure why in these days of cheap LEDs they persist in using insanely bright incandescent bulbs hidden behind semi-opaque covers for interior lights, but they do and those little bulbs can use a surprising amount of power.
BEFORE YOU USE THEM…read the owners manual regarding connecting order and disconnecting order.
If you have a good battery I would give it no more than about 48 hours before your car will not start.
Hint: the only source you need for jumper cables should be your own trunk*.
I’ve had the same set of cables for 30 years; they’ve lived in a lot of different trunks, hibernating sometimes for several years straight…till the one time when you need them.
*that’s a boot, if you’re a Brit. 
Thanks for your input everyone. The car started with no problems at all.
Win, Win …