Before answering, I want to commend this question. The reason it’s a great question is that it means the person who posted it recognized that tradelines should be closely timed with a credit goal.
One more thing you should know. There is a difference between how long you’re an authorized user (actively at the bank) and how long the tradeline will be listed as an authorized user in your credit report. Both questions are answered below.
Tradelines for sale at the bank: Contractually, we guarantee 1 reporting cycle. This means you will be added as an authorized user, we will verify that it has reported to your credit report. Once it has reported, we will instruct the primary cardholder to remove you. This usually happens within 30 days. Sometimes it takes two cycles. So, the answer is that you will be actively listed as the authorized user for 30 to 60 days.
Tradelines for sale on credit reports: Once you’re added to the tradeline and that we’ve confirmed the reporting, you will be removed. Now, the tradeline listing in your credit report will remain for a very long time. We have no control over this duration. Neither does the cardholder. Neither does the bank. It can last for many, many years. However, we wrote an entire blog post on this specific topic, which you can read here.