[Dorchester]

A while ago when firing up the missus' 25 for the first time I heard the dreadful "click click click".
I was very surprised. The VARTA battery wasn't that old.
But after a close exam in the 25 book, it appeared that it had been fitted on the 1st of November 2019.
Hence 5 years and half. Not too bad given it's the daily car.
But I dislike lost battles and despite charging the car with a so called intelligent charger every time it's not used, I tried the repair mode.
Once I'd tempted to save a desperate battery (my 214 cabby old one which had been fully discharged several times because of a dying alternator) but to no avail.
BTW it would be interesting to see whether this repair mode is a marketing fib or not.
The charger worked on the whole afternoon and the following night. I didn't want to interfere in the process.
Then the day after, the battery being standstill I swapped the repair mode for the normal one.
A fortnight after, so far the battery looks as new and works a treat: may I wonder if I can hope 5 more years?!
It would be nice to get 6 or 7 years in total, who knows...?
I'll keep you posted.

[Dorchester]

Finally the battery died yesterday after 5 years, 9 months and 4 days. Not too bad.
I ordered the same day a 52Ah battery, Varta C30 that replaces the previous C6 which came home within 24 hours!
Nevertheless I'd a working spare one from my P5B (age:4 years and a half). It's longer and more powerful (72Ah) but surprisingly it fits nicely in the tray.
The missus'25 started up at once.
I'll keep that larger battery during winter and will wait next spring to swap with the new one if possible.

[CoupeFan]

I'm ashamed to admit that recently I managed to run my nearly new battery totally flat. I thought the boot was closed but it wasn't and the light in the boot was still on and it, and the alarm, managed to run my battery down in just over a week until it couldn't even produce 3 volts on my voltmeter when disconnected.

At that low a level the small charger that I bought to keep the battery topped up on my Tomcat simply didn't work, its on-charge indicator LED didn't come on. Fortunately I do have another, much newer charger bought with recharging a start/stop battery in mind. I connected that, selected repair mode for a conventional battery, and it eventually brought the battery back to life with it showing 100% charged much to my relief.

But noting your experience, I will keep an eye on the battery in case letting it go so flat has done long-term damage.

[CoupeFan]

An update, for what it's worth! I don't keep the trickle charger permanently connected when not using the car, but do try to make sure that I use it weekly if I haven't driven the car. So far the battery is recharging satisfactorily. So it looks like I did manage to bring the battery back to life withoit too much damage.