Interesting conversation. Since I've been driving a few months short of 60 years, I can certainly speak from experience. For the record, I have yet to wear out/nor replace any clutches.
I too am from the camp wherein my father taught me to "use your gears to slow down because gasoline is cheaper than replacing your brakes".
Now then, I just paid $3.85 per gallon to fill up yesterday and that's roughly 20 times as much as when the lesson was given.
However back in high school I earned $1.50 per hour working at Foster's Freeze. While the average dealer's non-supervisory workers made $2.16 per hour out here in the West during 1962.
So, based on my history of never having had any clutches wear out in 60 years of owning many many vehicles (as many of you in the club know, I have a history of BUYING vehicles but seldom selling them) but I have had a couple of brake jobs,
I'd say my dad's advice was good. Even at $3.85 per gallon, gas is still cheaper than a brake job and I have NEVER had a case of "brake-fade" while coming down a long grade on a hot day.