Expiring bookmarks (temporary bookmarks)

I would like to be able to make bookmarks that expire after a set amount 
of time.  For example, set a bookmark that will self-destruct in 7 days. 
  Sometimes, I am looking at something, like a forum topic, and want to 
keep track of it for just a couple of days.  After a while, that topic 
might become irrelevant and the bookmark will just sit there, collecting 
dust.

Thanks,
Lou