This is at tough situation. As you must realize, the time to fight this was when you were sued, but instead, a default judgment was entered against you. You mention an attorney who advised you, but don't explain what if any role the attorney had in letting the default get entered.
You have a right to ask a credit reporting agency to verify and investigate adverse information on your report, but from what you say, the agencies are truthfully reporting that there's a judgment against you, and they're not going to look beneath the fact that the judgment is there.
Default judgments sometimes can get set aside, but there's a lot going against you here if you try that -- esp. the long passage of time and the fact that you paid off the entire judgment apparently w/o meaningful protesting at the time.
Is there any glimmer of hope? Maybe. Just possibly there's fresh evidence that this particular credit purchaser (I know nothing about it and am not making accusations) was engaging in some widespread fraud or other wrongdoing. You might research whether regulatory agencies have taken action against it or whether it's been successfully sued for abusive practices. Just possibly that could amount to some fresh evidence that would persuade a court to set aside your default judgment even at this late data and allow you contest what you say was a bogus claim. (Attorneys here -- attorneys generally -- mostly don't like recommending taking action against other attorneys. I don't myself. But you brought him/her up. If you really are in this fix because of incompetent work by an attorney you hired, you may have an action against the attorney.)
I am not familiar with California law, but tend to agree with my colleague that as a general rule (and certainly in Ohio) getting a judgment vacated after the passage of this much time is likely going to be a challenge.
If your question is how long can this adverse information plague your credit report, judgments may be reported 7 years after longer of date of entry or expiration of the applicable statute of limitations. Here is a link that may be helpful regarding when the law requires negative information be removed from your credit reports. http://www.ohioconsumerhelp.com/sub/obsolete-CRA-info.jsp;jsessionid=D2D41BD49868D8295FFA418014D1AF9E
All the best to you.
NOTE: This Answer does not constitute legal advice. Every case is fact specific. To render a legal opinion, an attorney must engage in a consultation with a prospective client and review any pertinent documents. This communication does not create an attorney-client relationship with Attorney Amy L. Wells or WELLS LAW OFFICE, INC.