Should a chain be replaced even if it's not stretched?
The 2000 miles is an estimate of when the chain will stretch.  Your chain may last longer than that.

As far as replacing it goes, I think it depends on your financial situation.  If you can easily afford a new chain, I recommend buying one.  A replaced chain means that you don't have to worry about your current chain stretching beyond the limit and damaging your bike.

If your budget makes buying a new chain difficult, you'll be all right to keep riding.  Just check the chain stretch every so often to determine when it's getting near absolutely necessary to buy a chain.