Re poly arb's...
I had a set of these on the shelf, and I've had to park my car partly in the drive for some time. This means one sides front suspension was compressed, the other extended.
I also had problems with a god awfull floating feeling from the front end on some road surfaces at the start of most journeys. To the point I turned round, headed for home, jacked the front of the car and searched for suspension faults. None found.
After some time

I decided to fit the poly arb's. My theory being that the twisted roll bar caused by the parking position, was compressing the rubber arb's which took some time to recover.
Anyway, once fitted the floating sensation has vanished.
I do agree though that, as Kev would say, we're entering a world of diminishing returns fitting further oe replacement poly, once the front wishbone poly bush has been fitted.
The gains are minimal. But there is some improvement to be had, although I can't say I've noticed any less body roll. The extra control seems to come in an almost level body position.
As said, there was zero signs of wear on the old rubber bushes, after 107k in my case.