What is the use in keeping it open when no one will ever look at it again after it goes stale? It still exists in the system if you ever wanted to find it again or if someone reports the same issue again. But after a certain time without reconfirming the bug exists, there is no point investigating because you will never know if you just haven't found it yet or if it was fixed already.

See my reply to eminence32 - bug tracking serves as a list of known defects, not as a list of work the engineers are going to do this [day/month/year].