Every time you use yum to install and/or update packages, it logs to /var/log/yum.log. A lot of people don't want to rotate the file a lot as they believe (incorrectly) that it is their only source to the history of their yum tasks. They may even believe that it provides a way to restore your rpm database if it gets corrupted - it does not.

I do recommend keeping your complete yum history as it doesn't grow a lot, unless you reinstall packages a lot.

For a rich interface to your yum history, I suggest you use yum history.

By default, your yum log file is rotated yearly, and even then, it only rotates if the size of your log file exceeds 30 KB, and your logs are only kept for 4 years. Usually, this is enough in the physical world as physical servers tend to be replaced every 3-4 years. However, virtual servers have the potential to stay "alive" beyond these 3-4 years.

/var/log/yum.log {
    missingok
    notifempty
    size 30k
    rotate 1000
    yearly
    create 0600 root root
}