I used to be on a mailing list that was put out by the Pumpkings of CPAN that showed what modules at what version were released onto CPAN. I also used to have have script that I ran once a week that queried the most recent version of the module list to determine if the version I had was up to date or not. I did all this when I in charge of maintaining Perl modules for a major financial firm which wanted all the CPAN modules to be no more than one week out of date. Huge PITA if you ask me.

Nowadays I don't bother worry about updating modules unless there's an issue that requires I update a particular module.