When I advice my client to do so.
New vehicle, stock battery lasted 40,011 kms before it died.
Installed 1st Century Battery and the mileage clocked 49,434 kms (odometer 89,445 kms)
However 1 month before that, I had instructed the owner to replace but he decided to delay the replacement. As a result, now the Charging Test when conducted shows a LOW result. It's quite impossible now for the 2nd Century Battery to even achieve what the 1st Century Battery did since it's Charging Test is LOW now. Not to mention battery warranty also void already.
Kejap let me trace back the record for the SoH.
4/8/24 SoH 75%, instructed the client to replace but he had better ideas instead.
By the time the replacement was done 29/8/24, SoH 68% and now the Charging Test is LOW.
Same owner, asked him to replace on 19/11/24 SoH 71% but thought he can delay until it died on 4/12/2024. SoH 24% This time what happened was even with the new battery inside, it managed to start once after that it could no longer start anymore.
This guy has a brand new HRV also and I wonder if he still dares to delay battery replacement onot when the time comes.
How you manage to go to 20% is beyond me.
I do remember this rich guy with many vehicles. He has the old Camry model that I liked very much but no money back then. Use until battery Kong. Rich people mah, where will listen to poor people one. When I opened the bonnet, already got strange sound. Called the Mrs to enquire if this is how their Camry operate. Said no. Made a video and sent to her hubby. The test revealed SoH was 8%. Guess what, Charging Test is already at nyawa nyawa ikan before it loses its battery warranty and it also suffered a blown headlight.

I am no smarter than the testers I use and thank God I have got some good customers who are willing to follow what my testers say, at least to compensate for those who don't. At least there are still level headed customers around, just that I have to find them only. Yang lebih pandai daripada tester, please don't call me.
The battery I am using has been charged frequently, that's how it survived 4 years+. Even at 20% SOH (as estimated by my budget analyzer) the car starts and runs fine.