Thanks for the suggestions

I am not a stalker on the internet or on this site. I confess to using the site and not registering as a user. I finally did it to thank a lot of you for your ideas/experiments/experiences/observations on how to drive a Prius Prime safely and get good gas mileage.
This Prime is my third Prius (or is that Prii) - #1 a 2004 - 3 (now my daughter's), #2 a 2014 V (my pickup truck). I have enjoyed driving them all and have my own techniques for getting good gas mileage. The Prime was quite a different animal and over the first thousand + miles driving it and using it with and without charging, I have done a lot of single trip tests to see how to get the best mileage with it.
I will make a list of the suggestions I have found most helpful and post them. Many will not be original on my part and I will not be able to give an attribution of where I read it, but if you recognize your thoughts, I do appreciate them. My one conclusion so far is I get the best mileage (when fully charged) on this long run by just treating the Prime like a regular Prius (with a really big battery, relatively speaking) in hybrid/eco mode and saving battery wherever possible for any of the slow speed driving sections. I let the Prii-brain (that sounds a bit like Mad Cow disease) do most of the "thinking" so I just drive. This makes my wife much happier to boot. I do intercede on a rather long, tall hill and put the car in EV mode. This appears to be the best option after trying several different ways of approaching it.
The results for the last tank of gas are about 71 MPH with 4 charges for just over 700 miles of travel in cold conditions (ave temp about 25 deg F). Respectable performance. The bulk of the driving is a 40 mile drive each way (for 80 miles total) on state roads thru towns and with open stretches (with 50 MPH limit). There are lots of hills which are good and bad. The best mileage without a charge (starting on "reserve" battery level) has been 67 mpg on the 80 mile trip at 40 deg F. I realize that by having a "longer" trip it obviously helps because the car is not having to warm up repeatedly (thanks to reading many posts).
Again, thanks for tips like turn down heater, don't use defroster, start in hybrid mode to warm up then go electric in slower speed sections, etc. With these, I have been able go up my learning curve quite quickly.