9 years old...
I have the original battery in 2015 Audi Q5. The car was in CA for the first 3 years and since then in MI. Car has about 65k miles and no problems starting whatsoever.
It is parked for 2 weeks quite often with no interactions. Alarm is not armed.
So they may last longer...
As for you, what that could be?
Maybe a loose connection?
Can battery die all of sudden? Yes, the cell will short when you are driving and it will discharge quickly once parked.
If the battery was left completely flat for more than a week, it will be a toast. No charger will bring it back to life.
Yes, you could rinse it with DI water and charge it, repeat 3 times and then flood with acid. I had done it years ago. Worked. But nowadays - no access to cells. Plus getting sulfuric acid is not easy.
If you think you have a leak somewhere (current leak), you could use this gauge. I chased my daughter's car issues with it.
https://a.co/d/6YPXpbk
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