If they're certain his wife can't have more kids, it seems like there's really no reason not to...and if they want more in the future, there's always adoption. That said, my husband has considered having a vasectomy three different times...and every time he's put it off or reconsidered. I'm glad he did because now we can have a child together, and we now have one on the way, but on the flip side he'll be 51 in a couple of weeks and now has six kids because he didn't make up his mind on it. Three are adults and the sixth isn't born yet, so it's not like it's an overwhelming number, but he's also starting to feel like he's spending his entire life just raising kids. When it comes down to it, I suppose it is a very personal decision and there are any number of factors that go into making it.