If one car headlight burns out, should the other also be replaced at the same time?

Change both. My mechanic does the same. I guess it pays in the long run.

Apparently, if you change them at the same time – they are going to die around the same time – so logicly you shouldn’t bother “saving” as the other will die shortly after anyway. It’s the work, and effort and time that costs – not the bulb which is pennies.

Headlights are easy to change. I don’t see much of an effort if you hold back on one and wait for it to burn out.

Tires are a whole other thing. They should be replaced (at least) in sets of two.

No. Only do that with socks ;)

Don’t waste the money. Change one.

I agree with @ChazMaz.

I can’t see any economic or efficiency benefits for changing both headlight bulbs at once. Replacing two separate bulbs is still two jobs, and the only labour saved by doing both in one go is that you open and close the bonnet just once, which I don’t consider to be very much effort at all. I don’t think it’s that sensible to change both bulbs at once on the assumption that their lifespan will be about the same either – I don’t think lightbulbs are that predictable, and bulb lifespan can vary a lot. As inexpensive as bulbs may be where you live (they are a rip off here!), I’d consider it a bit wasteful to discard a perfectly functioning bulb.

Tyres are a different matter entirely. The wear on tyres on the nearside and offside of each axel should match, so that you have the same level of grip for the tyres on each side of the axel. If you change just one so you have a new tyre and a worn tyre, the wear of the tread for the tyres on that particular axel will be uneven. The handling of your car will be altered when driving normally, and in the event of an accident, you’ll be far less likely to skid in an even straight line. Therefore, you should change tyres in pairs, and ideally, change the lot in one go.

For any other kind of light bulbs (auto tail-lights, say; or the multiple-bulb light fixture hanging in your dining room) I would change one at a time—spending money on an as-needed basis and squeezing maximum life out of working bulbs.

But my experience with car headlights is different: when one headlight burns out, the other goes surprisingly soon as well—evidently they have a more uniform lifetime than other kinds of lights. Plus there’s a safety issue—a burned out headlight is more than a mere inconvenience. I’d replace both at the same time.

Obviously not. I’ve only had a headlight burn out twice in many many years of driving. Both times I asked if I should let them replace both, and the response was no.

I have always changed both when one died. My father preached this for everything. Headlights, turn signal lamps, running lights, I once had to replace all the dash lights. (I will never EVER do that again) I have tried to see the lights in the back of the instrument panel of my truck and couldn’t even find it!

If they are hard to reach bulbs I would say yes. Headlights are generally easy to get at so I personally just change the one that’s bad only but keep a spare on hand. I have already had the untouched headlight bulb last a very long time after I replaced just the bad one only. It’s your call however but that’s what I do.

I’ve never had an issue with replacing just one.

Then again, I have always had used cars over 10 years old, so it’s unlikely that my bulbs were the same age anyways.

I’d only do that with dashboard lamps, being such at bitch to get at. The other lamps I carry spares for in the tool kit and change them as needed.