I'm down to 1 mug a day of regular coffee. I don't need it to get going, I have hot lemon water first thing (learned that from my Grannie), then breakfast, then the coffee (with the paper or the Olympics). The rest of the day is decaf, or tea, or lemonade, or whatever. I am not that great with milk any more digestively, but cream is fine (10% and up). This seems like the optimum amount for me, I am OK with half that if schedule warrants but it feels good at this level.
Coffee and cream never affected my GERD, but sugar and carbs and wheat sure did. Everyone's body is an N=1 experiment in finding what works best ;-)