The value of getting the last word in is rarely positive.
I have engaged in a number of email threads which roughly follow this pattern:
POI (Person on the Internet): Technical thing, technical-political thing, wrong technical thing.
Me: Actually wrong technical thing is wrong; have you tried right technical thing?
POI: Right technical thing works; technical-political thing.
At this point I have the option of continuing the conversation... but note that I have not been asked a question. Nobody has been asked a question, really.
It's a good point to stop -- especially if I disagree with technical-political thing.