Some of the best ways to get/give oral is to have something to mix with the pleasure. I may be new to PE, but I do not consider myself a newbie when it comes to satisfying a woman, and myself

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Mix Pain With Pleasure
Have her scratch you
Hang onto a pullup bar with your arms
Add Some Flavor
Mint - My preference is Dentyne Ice
Whipped cream
Syrup
Hot and Cold
Be somewhere fairly chilly, like a lake or somewhere you like at night to go "stargazing"- I brought a blanket or two for her. She was covered up and when it was my turn my chest was exposed to the nippy air. Having one part of you hot while the other is cold, feels great.
Those are just some suggestions if you want to get better head. I don't know about it making it shorter or longer. My longest is 1 hour and 40 minutes.