It's really strange.

I did not notice any problems before the new battery.
I replaced it because the one I had was fairly old and deader than a doornail. I think mostly from sitting in the garage during our last cold spell.

What really strikes me as strange is that these are coming on without any ignition switch engagement.

When I hooked up the termials, I could hear a sound like a set of contacts being energized.

I put a new alternator in the car in '01.
I also replaced the external voltage regulator at that time.
I've always had an "issue" with headlights dimming and brightening at will.