In average, blowjobs can last between 15 and 20 minutes, but there are many factors that can affect this. Always remember that communication is very important in order for you and your partner to be comfortable and to know what you like. Plus, some men take longer to finish than others. I have a friend who needs like 30 minutes, others probably finish in 10. It really varies on the guy and how comfortable both of you are, not only your "skills" as someone else said. It's all about trying new things! And always remember to do it with someone you feel comfortable with. I hope it helps!