Matt pretty much covered it, properly cared for poly will last a long time. On the “squeaking” thing- if your poly bushings are squeaking, they need to be lubricated. It’s that simple. Poly functions a little differently than rubber. The biggest difference in function is at the LCA bushing in these cars. A rubber bushing is friction fit into the shells, nothing spins or slides. Every bit of suspension travel at the LCA is from the bushing flexing between the inner and outer shells. Which is why the LCA pivot nuts must be torqued at ride height. The rubber can only flex so far, the LCA must be in the middle of its range of travel when everything is torqued so half the flex is up and half the flex is down. Otherwise the bushing tears.
With poly, you should have a tight slip fit into the shells and onto the pin. As in, no play, but some slip. That’s because the poly will not flex to create the suspension travel. Instead, the bushing rotates on the pin. That’s friction, and that’s why they need to be lubricated. Unlike rubber though the LCA movement will be exactly the same through the entire range of travel. With rubber, the further it flexes the more resistance you get, until it tears or binds. So with poly you get a more consistent suspension reaction and feel. And less deflection, so fewer changes in your alignment as the suspension works. And you can torque the pivot nuts whenever you want, doesn’t matter.
Because of the differences in how the bushings work, I always recommend adjustable strut rods and greaseable pivot pins with poly LCA bushings. Having the ability to grease them will ensure they last a long time (longer than rubber). And the adjustable strut rod is necessary to adjust the strut rod length so there is no binding. The factory strut rod length was “one size fits most” and depends on those big sloppy rubber bushings, if the length wasn’t perfect the rubber just flexes more. With poly the length has to be correct or you will get binding. But, If you tune the strut rod length properly you’ll have no binding or resistance to the suspension movement, which is much better than you get with stock bushings.
The easiest way to look at it is that rubber bushings on these cars are maintenance free. Install them and forget about them until they fall apart. Poly bushings are not, they need to be lubricated just like ball joints and tie rod ends. Maintain them and they’ll last darn near forever. Slap them in and don’t maintain them and they’ll squeak and then fall apart. And then you’ll be one of those guys saying poly is terrible because you installed them incorrectly and didn’t maintain them.
