Also use your router just set a permanent lease (That's what I did) thus no change needed on OS but IP never changes :-)
if your have many rigs, it will get you mad.. .haha. it is good idea for little rigs.
Not necessarily. Its one of those do it once and never have to worry about it things. You set the router to assign an IP address to a certain MAC address and every time you plug that machine in, the DHCP would assign it that address, even if you re-install the OS.