I do 80 miles a day, five days a week...mostly highway.
The thing with highway commutes from what I've experienced is this...
It gets up to operating temperature and it stays there. There's nice air flow across the radiator and you're at a nice steady speed. You're not using your brakes and the suspension isn't being stressed much from the braking or cornering. It's easy. It's straight ahead driving. You're not accelerating hard from dead stops. And you're at a pretty constant engine RPM, usually lower, with the very gradual/occasional uptick in RPM's.
The downside is paint. The stuff that gets thrown onto your grill, windshield and hood, isn't ideal. Paint chips, lots of them. Cracked or pitted windshields? I don't think I can make it through one year without something hapleneing...a crack, a rock hits it, sand splatters all over it. Constant, but worse in the winter. [censored] I ven had a turkey hit it. A TURKEY! Another thing...engine RPM...lower constant RPM, might lead to a little more oil consumption from what I've read. Not sure.
Overall I'll take highway commutinover anything else.