How long can credit report agencies keep bad credit on my report?

Most things can stay on for 7 years, some (like bankruptcy) for 10 years.

The responsibility to remove bad information from your credit report mostly belongs to you. The credit bureaus primary job is to satisfy the demands of their clients, your creditors, while continuing to obey the law. Expect the credit bureaus to work to please their customers as being more important than complying with the law & you will understand why obsolete info continues to remain on your credit report - working for free for you & me isn't as important as working for a paying client. Learn how to file disputes with the credit bureaus and dispute irregularities on a regular basis. The internet is filled with information about how to do this & I can tell you I was able to remove 5 old & negative items from my own credit report by simply following instructions. Free credit reports from the 3 major credit bureaus are available through www.annualcreditreport.com Best regards.

This is not really a bankruptcy question, but it is 8 years from the date of last activity. In other words, as long as the creditor keeps updating the report, it stays on for another 8 years.