New 2005 Prius owner - any advice re: doing lots of highway miles

There are routine maintenance items that should happen near 100,000 miles and 7 years.
Ideally you should change the Transaxle fluid with new WS ATF every 60,000 miles even though this is not on Toyota's scheduled list. If they haven't, now is a good time.
Brake fluid absorbs water from the air then rusts your brakes internally, how long this takes is dependent on how humid it is but 7 years is very likely time to bleed and refill AT THE DEALER.
The 12 volt battery should be tested to see if it is doing well.
Spark plugs and PCV valve should be coming up on changing.
Examine the rubber hoses and coolant.

None of these are specific to highway miles except you are farther from help if they strand you. Except the brakes, all are DIY projects depending on your skill level. Prius brakes require dealer software, it is not a skill issue.

 

Mileage tips:

• Keep it under 65 MPH.
• Go easy on the A/C. Meaning, if it's a 90F day, try and set the A/C to an auto temp of 77F or more.
• If you don't have extra gauges to let you know what's going on with the hybrid system, cruise control is your friend on the highway.
• Keep large buffers between you and the next car in front of you.

I drive about 110-120 miles every week day, and right now I'm averaging about 57 MPG with a 75% highway commute.

 

Welcome to PC - Congrats on the New Car.
As for MPG
1 Drive the speed limit.
2 Drive like u have no brakes.
3 Learn to anticipate stops and slowing ahead.
4 Tries at 42/40 PSI.
Best of Luck to You!

 

So, slam the car into a ditch if there's a need to stop in a hurry?

(You might want to explain yourself a little more. Not everyone is savvy with hypermiling techniques)

 

Just maybe if you ' need to stop in a hurry' it is the wrong time to be improving MPG.

 

I mean coasting to a stop at lights and coasting when traffic ahead is slowing down. Like you would do if you had no brakes.