Static IPs are like you said, static. They do not change unless you unplug your modem for a long period of time or you have your ISP change it.
At times, the IP will change eventually. (I'm talking about Residential Inet Service Providers). If this static IP belonged to a server you were renting
from a datacenter, then that IP will never change.
Dynamic IPs will always change. Shutting off the computer, resetting the modem or anything that disrupts the connection will change the IP.
Getting down to the original question.. If his IP is indeed static, then using hamachi is completely useless. He's better off just forwarding his ports and
turning off his firewall or adding rules to it. Then all he would have to do is keep his External IP in the realms table (not configs) and it would be accessible.