How long can a car battery last?

3 to 4 years is average but I did have a Panasonic battery last 7 years. If you ever run the battery down you just shortened it's life.

It depends on the battery type and how it was treated during it's service life. I have a 6pack style AGM in a rarely driven sports car that is 10 years old and still works fine because I keep a AGM smart trickle charger on the car when I'm not using it. The average flooded wet cell battery is only good for best 4 years use unless it has service caps, then you may also get 10 years service life if you only add distilled water. The newer cap-less style calcium stabilized lead selenium type flooded wet cell H2SO4 (sulfuric lead acid) batteries are basically a 5 year max life and it's gonna be a trash it out deal.

Car batteries take a hard hit when the A/C is running in traffic, the constant inability to charge whist running fans at stop lights takes a big toll on the eventual lifespan of any type wet or gel electrolyte cell battery. Interstate battery is the only company selling service cap batteries these days in the US, a good investment if you plan to get the best lifespan out of a replacement battery with hydrometer servicing. A battery acid specific gravity tester (H2SO4 hydrometer), small bottle of H2SO4 acid and box of baking soda to flush the hydrometer out costs $5, a new car battery is $125-200+ depending on the size and quality you choose. Find your nearest Interstate battery dealer if possible and get one in your size with service caps, the investment will last you the cost of 2 cheap calcium stabilized H2SO4 replacements that only last about 3 years.

AGM safe charger to maintain your battery when left idle - Schumacher SEM-1562A-CA 1.5 Amp Speed Charge Battery Maintainer

2/3 years

No, they last about 5 or 6 years regardless of use.

I believe the average life expectancy of a car battery in a modern automobile is 5-7 years. Just because there is no receipt for a new battery doesn't mean it wasn't replaced at some point.

One of my bikes has a battery 12 years and 3 months old and has done 50 000 mile. Anything over 3 to 4 years is an absolute bonus.

Could be.

It's possible, but unlikely. He probably just lost the receipt for a replacement.

Yes that is possible

Once I had a Yuasa car battery last for 12 years.

It is POSSIBLE, but highly unusual.