I am not sure that there is any way to have the forum software automatically close threads after a certain time frame.

I do agree on being kind to those that bump up old threads with new questions. We can ask them to start a new thread for their question in order to get more attention (and then close the old, bumped thread). Sometimes new users don't actually know how to start a new thread--that is a common question that comes through via the Contact Us form. So they might just need a little guidance.