2020 with <20K still going strong. Garaged.

 

I am still on original batttery on my 2015 nx200t

 

Think of how much stuff on your car requires electricity. So much stuff on the car won't work if the battery goes bad.
So, replacing it after the 1st sign of wear is wise.
Simply getting a low voltage indication on a voltmeter is not a good indicator of its health, but would mean your battery needs replacing, immediately.
The load test is the only way to know whether a battery is up to par.

 

2017 NX200t - just replaced a battery with Costco Interstate. OEM battery lasted 6 years and 90K miles exactly.

Due to very cold weather, at Costco today batteries were flying of the shelf like hot pancakes.