What kind of battery?
You are in a pretty stable environment temperature-wise, so you won't have those freezing morning slow cranking issues (all the sudden).
I say keep it for now and replace it when you notice a slower engine cranking at start-up than normal.
I believe in PM too, but get a lot of enjoyment from maximizing the life of my parts.
Keep jumpers in the trunk just in case.
I have a seven year old battery in one of my cars now. -still works
Of course monitor your terminals, connection/s to starter, and water level.
If you are really concerned slide by a parts house and have them toss a battery tester on and see. -should be free