the brakes are making loud screeches i associate with needing new pads.

but

the dealer says i dont need new pads
rotors arent warped or grooved.

so do i need new pads? oh, 34k miles

Calipers might be sticking.

I need to replace one on each car, actually both are sticking on the SSEi, even after new pads and flush.

there not sticking enough to worry just enough to making a metal noise when driving.

Calipers are not necessarily sticking, pads are not necessarily worn.

That squeaking is most likely caused by glazing. Glazing occurs when you are grannying the brakes etc. Try making a series of harder quicker stops and you should find that it goes away.

Mine were doing that too. Get some disc brake quiet, either the blue or the orange stuff, and put it on the back of each pad(part that contacts Caliper, not rotor)
While they are out, take some fine grit sand paper and clean up the pads a bit, remove the glazed coat..helps a ton.