Spirited acceleration actually doesn't effect your mileage as much as you'd be inclined to think it would. And that's the very reason that our extremely quick cars have such fantastic range.
Yes, during the very few seconds that you're accelerating, you're really chewing up the energy. But you are only doing it for a very few seconds. But you spend a ton of time at your cruising speed. And since going faster greatly increases your drag (hence, energy usage), the slower you go at cruise, the better your "mileage." Time-at-speed is the greatest factor for determining energy usage.
Also, the air conditioning is extremely efficient at moving heat around. Using AC when it's hot outside isn't going to greatly affect your energy usage. But in cars with resistive heaters (in other words, no "heat pump") using cabin heat in the cold will greatly affect your range; your car's stored energy can be used to either produce cabin heat or to move your car down the road.