"Two-and-done" is good, but many times you run into people who don't give a s*t about the outcome. They're just making their employer their own personal debate club. "Oh you think X? Then I'll propose Y. Let's have a debate! Yay!"

So always follow up after a "two-and-done" experience to see if the people who argued against you are suddenly disinterested in the entire project once they've won the argument, and do it your way anyway.