This is one feature that I wished that they removed from CPAN. Reviews don't generate enough traffic to be meaningful and when problems with a module are fixed or addressed ratings are not changed to reflect this.

A good example is Module::Build, it has a rating of 3. It is currently on revision 0.34 and got reviews as early as revision 0.19( which was in 2003). A person complained about the lack of PREFIX support and gave it a 1 star in 2005! I am sure over the course of 4 years that issue has been addressed but that rating is never going to change.

Ratings for CPAN modules are more like credit scores but they don't go away after 7 years. They just have no relation to reality, so don't worry about.