Just get a vascectomy?

http://www.plannedparenthood.org/pp2/portal/medicalinfo/birthcontrol/pub-contraception-vasectomy.xml
Hey, they're supposed to be the experts. I'd be willing to look at
another site.

| Can vasectomy be reversed?
| Sometimes it is possible to reverse the operation, but there are no
| guarantees. Reversal costs from $4,000 to $13,000 and involves
| intricate surgery. Success in restoring fertility is uncertain. From
|
| 38 to 82 percent of men with reversed vasectomies are able to cause
| pregnancy. The factors in this wide range include
|
| * the length of time since the vasectomy was performed
|
| * whether or not antibodies to sperm have developed
|
| * age of the woman partner
|
| * the method used for vasectomy and the length and location of
| the segments of vas deferens that were removed or blocked

In my cute little story, it was easy enough to state that:

<in 2063, all of the various STD's are either vaccinatable or curable
or both, and because the girls are taking birth control pills with an
effectiveness of 99.96% and the boys are taking birth control pills
(yes, male birth control pills) with an effectiveness of 99.96%,
meaning that the chance of both pills failing at the same time is
0.0016%, or less than one in a million. Even for sexually active
kids who start young, this would take a while.>>

But the technology isn't there yet.

How about this:

The guys get vasectomies in there early teens, but first they have
sperm frozen. Now, they can reproduce when they are ready. Ah, but
first we need more reliable sperm freezing. Probably have the male
pills by then. Even if the chances are one in twenty thousand, that's
pretty good. The one in a million from my story is, I believe, an
attainable goal, but we aren't there yet.