This question suggests using a tool or ruler to assess chain stretch to determine when to replace a chain. I have one such tool (Park Tool CC-3), and it tells me that my chain is not stretched even to the 0.75 level (is that %?).
My chain has at least 2,000 miles (~3,200 km) on it, so I am wondering if it should replace it just as a matter of practice (i.e., preventive care). I try to take care of the chain: wipe it down after rides, lubricate regularly (good advice here), etc.
So is it inconceivable that the chain is still in good shape after this many miles?
Is there any other reason to replace the chain other than elongation, assuming it otherwise appears to be okay?