Back in the dark ages you filled the battery until you saw a curved
rather than flat surface. Is it the same now? The battery in my 2013
Corolla was in it to my knowledge when I bought it in 2016 and I haven't
changed it. I drive maybe 4K miles/year in SoCal. The battery shows NO
hesitation whatever when cold starting. I'm amazed that the thing has
lasted this long, but don't see a a reason to replace it.

Added some water, but didn't want to add too much -- if there is such a
thing short of actual overflow. I liked the individual caps better than
the 3-cap thing it has now. Overnight charging (2A, decreasing) allowed
cranking at 8 and 9V.

Am I being foolish, or would it be foolish to replace this seemingly
really good battery?

--
Cheers, Bev
Organized people will never know the sheer joyous ecstasy of finding
something that was believed to have been irretrievably lost.
-- D. Stern

The Real Bev wrote:
> Back in the dark ages you filled the battery until you saw a curved
> rather than flat surface.  Is it the same now?  The battery in my 2013
> Corolla was in it to my knowledge when I bought it in 2016 and I haven't
> changed it.  I drive maybe 4K miles/year in SoCal.  The battery shows NO
> hesitation whatever when cold starting.  I'm amazed that the thing has
> lasted this long, but don't see a a reason to replace it.
>
> Added some water, but didn't want to add too much -- if there is such a
> thing short of actual overflow.  I liked the individual caps better than
> the 3-cap thing it has now.  Overnight charging (2A, decreasing) allowed
> cranking at 8 and 9V.
>
> Am I being foolish, or would it be foolish to replace this seemingly
> really good battery?

You could have a resistive load test done on the battery to help
determine its condition. Some auto parts places will do that for free.