After a vasectomy, how long until a man is permanantly sterile?

After a man has a vasectomy, how long will it take for him to progress permanantly sterile? What does he have to do to get rid of the sperm? How can a man let somebody know if its all gone?
A man is not for always sterile after a vasectomy until his sperm has been checked and he have shown to be sterile for two tests.

The first test is usually made just about two weeks after the vasectomy and the second test a day or two then if the first test proves to be sterile.

Until both tests come up cynical for live sperm, you should use some method of contraception to prevent pregnancy.
Usually a man is still fertile for three years after a vasectomy, though he can remain fertile until he would customarily become infertile.

The sperm are simply phagocytized, or "eaten up"/absorbed into the body after three months of being surrounded by the vas deferens.

Edit: Looking at other answers, I realize you may mean until the substances emitted during ejaculation are sterile. If that's what you mean't, than look at the other posts. But I mean't for always as in, even if the vasectomy were to be undo, would he no longer produce sperm.
I'm unsure as to how a man can tell when it's all over. I don't know if he can. By getting rid of the sperm I took to niggardly, what happens with the sperm that are still produced after the vasectomy.
Answers:    After vasectomy: In general after nearly 40 ejaculations the sperm count will be zero. So it depends on how frequent the sex the person is have before he totally empty his vas. Masturbation can be considered "sex" for this purpose.

Patients are other advised to have no unprotected sex after vasectomy until after 2 sperm counts are denial!! After two negative sperm count the person is "ineradicably sterile"! A man cannot tell that all sperms are own to have sperm count!

Hope this answer your questions.
usually they tell you to wait 6 weeks. Masterbate or hold other protected sex to get rid of the rest. The only route to tell if it is all gone is to look at a example under a microscope.

They tell you to use other forms of BC because within is a chance that the Vas Differences that were cut to manufacture you sterile grow back together and if you arent using other protection you know what that will give you contained by 9 months!

Good luck
Two clean semen analysis (about two months). But I was extra painstaking. I kept using condoms for almost a year to be safe. I go put a bet on and get a semen analysis done every five years.

You can't tell by looking at his semen. It is a popular urban fairy tale that sperm are white. They are far too small to contribute to the color of his semen.