Note that the default varies by implementation. Various versions of windows default to privacy extensions.
Privacy extensions means your IP changes regularly, usually once a day. For servers you don't want that, but for client PCs the tradeoff is different. If it bugs you you can set the IP address yourself.
Note the link-local address always includes your MAC address, but that address never leaves the LAN, and everyone on your LAN needs your MAC address anyway to talk to you.