I definitely see your point here. As certain as one might be at the time, though, it is still one vote based on the information available at the time. If an expert comes along and sees something that I missed the first time, I think it would be appropriate for me to re-evaluate my no vote in that light, plus any other information that might have been added to the observation in the interim. I can always re-vote no if needed.
That said, the pending overhaul of the notifications system may well address the issues in this request, in particular