Thanks for all the suggestions.
A little more info -
I've 4 decks to do, total ~ 1,000 sq ft.
In previous iterations of my decking preservation attempts I've gone from Thompson's water seal (good for ~ 1yr) to a Sherwin Williams (SW) recommended stain (2 to 3 yr) then was strongly advised to go with a solid pigment solution - on the theory that light destroys stain. So I settled on a SW SuperDeck Exterior Waterborne Semi-Solid Color Stain (this seemed to be a more of a paint to me) and this has held up really well for two full years on a small deck that gets direct sun from dusk to dawn in Virginia. There were some spots that had gotten stained by drippings from grilling chicken that peeled up the first winter, but a second application seemed to fix them.
Looking at this deck a few days ago it looked pretty close to what it looked like a week after application.
HOWEVER, as stated it's only been two years.
That said I've read of some new (to me) products such as
Gulf Synthetics Deck Revive. Resurfacer Coatings for Wood that claims to
Deck Revive actually fills in cracks and knots, locks down splinters and nailheads, and provides a new slip-resistant textured surface that lasts for years.
It's a 2 part mix that must be used the day it's mixed. And the entire process (pema bond + deck revive) done in a day or two.
However that requires prep with their "Perma Bond" and addition of 1 gallon of gloss exterior acrylic latex paint of any color. So cost comes out to
$250 Deck Revive Full Kit (Coverage: two coats will cover approximately 200 square feet.)
$100 Perma Bond (coverage 350-400 sq ft) so estimate $50/200 sq ft
~$50 gallon of exterior latex ~ 200 sq ft.
Total ~ $400 for 200 sq ft, or $2/sq ft.
Compared to SW SuperDeck Exterior Deck & Dock Coating which covers maybe 100 sq ft for ~$80 but might need more coats. So maybe $160/100 sq ft, or $1.60/sq ft.
I tried to find coverage for Cabot Australian Timber Oil, best I could find was maybe 250 sq ft/gallon for $56@ Lowes. That would be a clear winner on price if I could trust it.
More research needed.