Why don't you try a few scenarios out for yourself and see which is best? No one can answer what's best for you as your terrain, miles you drive, etc are all relative your conditions.
I personally have not driven on any fuel miles except one time where I ran out of EV miles 2 miles away from home. I've also had two EMM sessions.
If it wasn't for the stupid FMM every year that I've not had yet, I'd have anticipated not having any fuel miles at all as my 75 miles of EV range every day is more than enough for me.
I average around 60-65 MPH on the highway BTW. I'm "Voltser" on Voltstats.
There is absolutely no reason to use hold mode or mountain mode if you know you'll have enough miles to drive back and forth on EV alone. No matter what regime you are in, EV mode is always more efficient. Using the engine is only a "must" in my book.