Pretty straightforward, simply add the following in your .bash_profile:
alias locate=’if [ $((`date +%s`-`eval $(stat -s /var/db/locate.database); echo $st_mtime`)) -gt 3600 ]; then echo “locate: db is too old!”>/dev/stderr; sudo /usr/libexec/locate.updatedb; fi; locate -i’
Note: Run source ~/.bash_profile to reload.