This is exactly how I have been driving all my Boxsters since the day I took ownership of each, gas mileage is a secondary consideration for me in these cars, but even with this approach I have always been satisfied with their range on the highway.Nobody asked for this, but I'll reiterate my previous advice on how to drive a Porsche for engine preservation.
Don't lug your engine!! Lugging your engine can cause bearing damage and piston scoring, long term. Get the revs up. These are Porsches, FGS. Cruise around town at 3500 +/- rpm, and on expressways and shorter trips at 3000, and on longer Interstate drives at 2000-2500.
Use plenty of downshifting, for engine braking, to keep cylinder walls lubricated!! Frequent engine braking sucks oil up the cylinder walls and will go a long way to prevent piston scoring. And guess what? Your brakes will last longer.
And, FGS, turn off that stupid greenie switch that allows coasting and shuts off your engine during stops!! If you are focused on gas mileage, get a Prius or a Volt or whatever else. Thank You.
As a retired engineer and lifelong gearhead, that's my experience and considered opinion. And I'm sticking to it... :gossip:
As for RPM, I love the flat-6's sweet song either going up the scale or coming down so when ever I can we work together to enjoy the drive...