I still think that expecting people to clean up 
their own images will be fruitless.  You will end 
up with lots of dead images and will ultimately 
have to wipe the board eventually anyway.

You could either bump the time limit out (say, to 
a month).  Or you could take your e-mail idea and 
modify it.  Send the automatic e-mail out just 
before the time limit is up and make it really 
simple like, "Just click this link to keep your 
cels active for another month, or do nothing and 
they will be deleted."

With your version, if people don't care, change 
e-mail, etc. then the dead images stay on the 
site.  This way, the person has to stay involved 
to keep their ad running.  I *STRONGLY* urge 
against any online system that relies on everybody 
showing self-responsibility.  It just won't work.

JP