regular kernel updates are great, but having 3 years of kernel updates on one hard disk is not. chances are you are never going to use any of the 10 or 20 that you installed last year. if everything continues to work fine, why would you?
you can obviously use a package manager, such as synaptic, to uninstall unwanted programmes. quite often you might find a few other programmes that you didn't know you had still and want to get rid of. but it's generally easier to just use the command line to remove things quickly.
use this command:
dpkg -l '-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d' | xargs sudo apt-get -y purge
i use this command in ubuntu and i'm pretty sure it will work in derived versions, but results may vary!