After my 3rd I thought I would never want another bub...but after 7 years I desperately wanted another one, and that's how Jack came about. Now Jack is one and I am already contemplating the next, LOL.
I think if you are still not 100% sure, you should not go through with the snip...it is so final. Only do it once you are BOTH 100% certain.
Marlene... this is exactly why DH and I reeeeeeeeally want to wait. I was certain I was done with having babies after my first 2... then when my DD was 7, we decided to start trying again. If we'd done something permanent, we wouldn't have our DS2 here with us now.