When someone asks you, "How long do credit inquiries stay on a credit report?" Be sure to tell them that while the fat cats will not dump the potential damning inquiries for two years, with a little leg work (that's code for money), and a lot of elbow grease (that's code for, be prepared to make a lot of calls), you can get rid of inquiries yourself.
Step One: Request copies of your credit report from all three of majors. Each report will include an inquiry section. Now the inquiry section will include two types of credit inquiries, those that are promotional (you were selected as a part of a cattle call and mass mailed pre-approval applications) and those that are not promotional.
As pesky as those mass mailings can be, it's the latter that you should be most concerned with. The Mercedes dealer you pestered incessantly the same week that you applied for store charges at Arben B, Bebe, and Nordstrom's, can be a problem. If you have not applied to some places not listed as promotional inquiries, they've got to go too. The first step is finding out what's in your inquiry section.
Step Two: Locate the addresses of the inquiring creditors; this'll be important for Step Three. Experian is the only one of the three credit bureaus that lists addresses of inquirers. If something is on one of the other credit reports that does not appear on the Experian report (reports will not always have the same information), then call Equifax. It's almost a Herculean task to get someone on the phone at Trans Union.
Step Three: Once you've figured out which inquirers are causing you problems, simply inform them in writing that you would like for them to remove the inquiry from your credit report. This will likely cause an uphill battle, but a few connotations to the effect of "I sue," and challenging that you did not understand that you were authorizing an inquiry to be placed in your report (which is true) you can ultimately win the war.
So the next time someone asks you, how long do credit inquiries stay on a credit report, answer with, "Until they get tired of fighting."