A dynamic IP will only change if the modem / router is reset. It will stay the same for the duration it is left on.

This is why some people haven't experienced these problems, because nowadays modems/routers are rarely turned off, so you wouldn't notice the change in IP.

Also there are some isps that issue static ips, I have one and i didnt ask for it and no I do not have a buisness account.

A friend of mine has to change his password everytime his router resets because of his dynamic ip. No one is breaking into his account. He is on the ps3 with a security token too.