Golden advice my father gave me:
The second you start noticing any buzz it's time to ease down. There is still more alcohol in your stomach waiting to be absorbed so you'll continue getting more buzzed even if you do stop.
It's a great way to pace yourself.
Edit: my 2c is that you'll be drunk on two unless you really spread them out. Take small sips and use the buzz rule. They tend to be reasonably potent.