I have a static ip address,
so it doesn't need to renew frequently at all.
If you have a static ip address then don't use dhcp. Dhcp is only used to get a dynamic ip address. Think of your modem as an extension of your computer. If the modem has a static ip address, then your computer has the same static ip address. Just configure your static ip address in /etc/network/interfaces (at a terminal, type: info interfaces to find out more)