There is really no way to fake an orgasm by way of blowjob. If a man wants to fake an orgasm during sex he can, provided he is wearing a condom, or if he is super crafty and pulls out to pretend-climax into a near by bush or towel that he then burns.
 
But when it comes to oral sex, they're only two outcomes. Stop this isn't working, or stop this worked. In terms of easiness... that is a difficult question to answer, or rather, an answer that won't leave you satisfied. Some men do come quick. Some men don't. Some men sometimes come quick if the feeling is right. Some men who usually come quick won't come if the bj is awful or the vibe is terrible.

In terms of nailing down an actual time, ah hell, you've inspired me and I'm going to throw out a number. Eight. If your man isn't close to coming by eight minutes, it's time to switch up technique or ask him if everything's cool.
 
Above all else, the penis itself is a terrific indicator for how well the bj is going. It is man's measuring stick. If it's veering limp - not going so well. If it's building in stiffness and his body and breathe seems to move to your motions - 2 thumbs up! You are well on your way.
 
Remember, though, don't be so quick to blame yourself if the bj isn't going great. He can be anxious, drunk, depressed, hung over, insecure, or all of these things. It's a misconception that men aren't emotional creatures too. Often times, if he's not going to climax or even that hard, don't be hard on yourself. Stop the show and check in with the penis's owner.