I was thinking not waiting too long between pregnancies would be a good idea for those wanting more than one.. i think over time there may be a possibility of it closing up, getting blocked etc.. i saw on a site today about vas reversal "Remember that it will take time to conceive and carry the pregnancy to term so most men wont need another vasectomy by the time it is all over" ..
i took this to mean that there is a strong possibility of things closing over.. not sure what to think.. maybe some are luckier than others?