I know I wouldnt want to cut out that kind of option. Who knows what might happen?
Personally, Id rather use the pill or a condom over that. And eventually, she'll be past childbearing, and you wont have to worry about it anyway.
My Dad got a vasectomy when I was iiiiiin.... 6th-ish grade. He and Mom were convinced that they didn't want any more children after the 3 they had.
And then came the divorce.
Not that he wanted any more children to begin with, or that women he's dating necessarily would, either, but it's always always always a possibility. Especially since you're only 34 (he's nearing 50 now), you just never know what kinds of things will happen. I know, I know; you're totally in love with and committed to your wife and vice versa. But stranger **** has, and will continue, to happen.
On a slightly more ironic note, a mere year and a half after my Dad's vasectomy my Mom developed a condition (I think it was cyst-related; I was young then and they didn't every fully disclose to me what was going down) that necessitated the removal of her entire uterus. My Dad didn't say anything, but I knew what he was thinking.
A vasectomy can be reversed; however, if the reversal occurs several months to several years after the operation, the body will often no longer recognize sperm as "self-cells" and will proceed to attack them as if they were a bacterial or viral infection (this is an autoimmune attack). This makes the sperm nonviable and thus makes the man infertile (but not impotent).