Recently, a user asked a question which referenced another question three years earlier, and asked "Is this still true? What new research has there been?"
My first instinct was to close it as a duplicate, and recommend the use of bounties to ask for updates on the original question, but that seems rather unsatisfying.
As we get older, I can imagine this is going to happen more often. I am nervous about the site being filled with people re-asking the same questions. Also, three years isn't really a long time in science; it probably is a bit premature to be asking 'what's known now that wasn't known just the other day?' Nonetheless, in principle, it seems a reasonable thing to ask.
How would you prefer us to handle these questions? Mark a duplicate? Leave alone? Other?