How long do one REALLY have to keep old statements of any kind and Paper Stuff?

Seven years for bank statements. Longer for the others. It is better to keep the taxes forever. The payments on something can help for future reference to get credit. If you have to change car insurance, you need proof you had insurance to keep from paying more money to the new company. This happened to me. I received a bill from a doctors office that had been paid. I showed that it had been paid.