WG: HowTo: Scheduled User Management?

Hello,

I have a small app which manages users in a postgresql db. I use 7.4.2.

Yesterday I got this requirement that user accounts should be valid only for
a given period. When I create a new user I will have to have two timestamps
one with now() and one with now()+6 months.

Now the tricky part: The system should check once a day if an account is
still valid and if not it should set the account to inactive and notify
somebody by mail.

How is this done the best way? I heard some stuff about doing this with a
crone job, is this necessary (db runs on linux)? My app runs in a tomcat
server so it is available all the time. Is this a job for quartz API or is
there an easier way? What would you guys suggest?

Cheers,
Pete