Credit reports can be a bit of a balancing act. On one hand they need you to take out credit so that they (the big three credit reporting agencies) can see that you have a good payment history otherwise they have nothing to base a credit report on. But if you take out too much different credit too quickly then they can see you as being a bad risk for their clients thus preventing you from obtaining a good credit ranking and possibly favorable credit terms on future purchases.
The trick is if you are looking for credit, whatever it is for, then only apply for the credit that you really want. Don't apply for many different products so you have a better chance of one of them accepting you. Of course, it can be difficult trying to determine just how long do credit inquiries stay on a credit report and when you can start applying for purchases requiring credit again without it adversely affecting your credit history.
Although you may want to know and may routinely ask yourself "how long do credit inquiries stay on a credit report" for perfectly good reasons it is not always easy to get a straight answer to the question. Credit report companies can be very secretive about exactly how they compile their reports for very good reasons and are unlikely to give you any real help, information or guidance even if you are trying to find out why you have been refused by a merchant for credit.
For a general guideline as to how long do credit inquiries stay on a credit reports, it is usually safe to estimate about 2 years. And if you have been refused credit because of this it is usually a good idea to wait for about 6 additional months before applying again for another loan. Even if you have been applying for credit cards and are now looking for a mortgage the credit card applications will appear on your credit report for the mortgage company.
The best way to make sure that the credit check companies do not see you as having too many applications for loans is to not apply for more than one or two things at a time. That way they may see each application as separate and you will not look like someone who is just applying for a lot of different products or credit at the same time. Of course if you get refused for the loan you are looking for then you are free to always apply to different loan and credit agency or company. Just remember, it is not usually a good idea to apply for too many at the same time. This way your credit is much more likely to be looked at favorably by the credit report company.