BJs, titfucks, handjobs - they have one thing in common: the receiver can reach orgasm at any time and doesn't have to worry whether he lasted long enough for the giver to be physically satisfied. In my glossary a proper blowjob means oral stimulation of the penis until orgasm occurs within the mouth and said stimulation occurs until the orgasmic spasms subside. In contrast fellatio is simply stimulation of the penis with the mouth, but doesn't necessarily provoke orgasm. Not everyone agrees with my definitions, but I give them so you can understand my point of view.
My personal opinion is that six minutes is a long blow job because I don't try to hold back. Many people, myself included, believe that it should be easier to reach orgasm through a blowjob than through vaginal coitus. If you want to receive fellatio as foreplay and after that have coitus I suggest you either let your wife know before you reach the point of no return so she can slow down or turn the attention to an area besides your penis; the scrotum, thighs or abdomen for example. After a while she could return to your penis once the "danger" or eruption has passed. You could try having her use her hand(s) on you in alternation with her mouth. I find that hands sliding up and down my shaft and over my frenulum deadens the sensitivity of my penis. Again it is important to try this before you reach the point of no return because,as you might have noticed, once you reach that point it doesn't matter whether you stroke the penis with a feather or hit it with a 9 iron - you're going to cum.
Another idea would be for her to perform fellatio on you earlier in the game. That way if you blow your cork you can take your turn applying foreplay to her while your penis recharges so to speak. Then again, I often find that if I am not completely "sucked dry" I remain erect after a blowjob and am able to perform coitus on the same erection. You may be interested in

The Grunt Technique
It is in fact possible to separate orgasm from ejaculation. I arrived at this through practicing the "grunt" technique which relaxes the PC muscle. This is the opposite of the so called "Kegel" exercise which tenses the PC muscle.

In the grunt technique the man mimics the action of trying to pass a difficult stool and grunts in the same manner actually eases the tension in the ejaculatory apparatus thus allowing him to postpone ejaculation for a while. At first you might want to stop thrusting. If she asks what's going on, especially what the grunting is about, you can tell her. After you have done it a few times you know the muscles and don't have to actually grunt. With practice you should be able to postpone ejaculation and possibly ( in my case it happened) separate ejaculation from orgasm thus allowing yourself to have more orgasms in a session.

If you ever experience an orgasm in which you ejaculate, but continue to have an erection afterward try to be aware of what was happening, how it happened and your state of mind at the time. In the future you will want to replicate this. Have you ever had a double ejaculation?. By double ejaculation I mean that you ejaculated a little then stopped only to have a more satisfying ejaculation/orgasm seconds or minutes later. If you experience this then you are probably on the right track. The first ejaculation will relieve the pressure in the prostate and the rest of the ejaculatory apparatus. This will allow you to continue or resume thrusting until another or more ejaculatory episode.

I have had as many as six ejaculations in one lengthy session with the same erection. Another result that I have had from use of the grunt technique and the exploration of non genital orgasms is the ability to have several ejaculatory orgasms in a relatively short period of time while maintaning an erection.

I should add that just because it worked for me doesn't mean it will work for you. Your mileage may vary, as they say.

In the long run you problem is very minor compared to others' problems. If you read around this forum or practically any forum about sex you will find that the majority of wives will not give blow jobs! By your standards, which are the only ones that matter, your wife gives great blow jobs. Sit (or lie) back and enjoy. Try my suggestions and those of other respondents. Maybe something will work. If not, so what.
The rest of your sex life seems to be great.

> Is there any way to last longer while getting good head.

Use the information in this article and apply it to your problem.

Squeeze & Training Exercise for Controlling Premature Ejaculation

I believe you said elsewhere that you are in your thirties? If so, why worry about lasting 6 minutes. Rest up, hydrate and go forth and enjoy more sex with your wife OR and better yet, move on to the next stage and rest up while giving her bodyworship and outercourse! By the time she's ready, you will have recovered sufficiently to perform properly.

Please review my sticky posts (articles) on these topics fouund under Married & Long-Term Relationships.