I called Peak Tech Support. The guy recommended I use Peak Titanium. He thinks it'd be my best choice for corrosion protection and 15 year change interval. He said Peak Global Lifetime would be my 2nd best choice, Peak All Vehicles 10X would be 3rd best. He didn't think the Final Charge products (Global or Pro) would be as good, but he might have just said that due to his perception of availability, but I know I could obtain any of those.
Unless someone at BITOG knows a reason not to, I'm going to buy Peak Titanium.
He probably didn't recommend HD coolants for your 25 year old buick because traditionally, HD coolants are for HD applications.
That said, HD coolant formations have staying power in the marketplace. Peak changed the 10x forumation this year. Could easily change Titanium next year. The auto coolant market is heavily driven by simplifying to universally compatible coolants to reduce SKUs. For all the universal-ish coolants on the market, if they aren't controlled by a manufacturer spec, they are subject to change. That's one of the nice things about ubiquitous dexcool.
Based on EU push to get rid of EHA, I imagine we will see some reformulations in the passenger car lineup.
I would bet money Peak FCG, Peak FCP, Rotella ELC NF and other OAT non-EHA HD coolants will be around in 5 years. Why does that matter? Sometimes it's nice to be able to top off or replace a hose without a complete system flush.
You're overthinking this. Your car requires at most two gallons of concentrate. The cost delta is irrelevant in the grand scheme. It's a fools errand to trust any coolant for corrosion protection much beyond 5 years. Buy two gallons something good that is readily available and get a $4 hygrometer from walmart. Flush, recharge, test, adjust mix, and worry about other things for the next five years, assuming the car makes it that long without accident, fire, theft, etc. Chances are the car won't make it 5-10 years without winding up at some corner mechanic who puts universal green snot in the system after a minor repair.
I put three gallons of Peak FCPro in our diesel pickup truck this fall when doing a preventative water pump. It's $17 a gallon (concentrate) when it goes on sale at NAPA. I'll keep a spare gallon of concentrate in the camper for emergencies and I know the premix is on the shelf at walmart and all the other parts stores along our travels. It's a cutting edge PhOAT, non EHA. Good enough for 5 years, cross compatible with lots of other coolants if I am in a pinch and can't find more.
While we're at it, why not just reccommend Toyota pink or Mazda/Aisian Green? Plenty of non-2EHA coolants around that will provide plenty of corrosion protection for a 5 year interval and will assuredly be available down the road.