@slowmover --
Thanks for the reply. It seemed to include a lot of assumptions and advice based on those assumptions. I'm not going to argue with you on specific points in your reply, but I'll try to summarize the big picture:
We actually don't drive all that much, we already optimize several of the more critical things you brought up (minimizing driving, combining trips, minimizing cold starts, etc.), and our safety record speaks for itself -- zero combined accidents in the past 20+ years. Unless you count the deer that ran out of the woods and crashed into the side of our car at night about 15 years ago.
Furthermore, the hypermiling stuff is merely a hobby of mine, albeit one that arises due to an innate personality trait of perpetual optimization. I don't really do it for the sake of saving a lot of $$, or reducing carbon. I do it because it's an optimization problem and it really tickles my fancy. As you say, it's frosting. Delicious frosting that adds enjoyment to my life and additional purpose to any occasion where I have to drive.
One specific note: when I said my wife is "focused on other things while driving" -- I'm not referring to
distracted driving like looking at her phone, putting on makeup, or something like that. She's just focused on driving and doesn't really get a kick out of optimizing the FE. She's not really interested in creating a perfect scenario with no cars around so she can P&G to her heart's content. That's my bag, not hers.